HE CHEATED. I know this is kind of long but please read 😔

Hey guys, first I would like to start off by saying that I really do appreciate every ounce of advice that will hopefully be given to me.I know this might be kind of long but PLEASE READ 😔. I really need some help.My boyfriend and I have been together for a little under 4 years. We are high school sweethearts. We have been each others first everything. We both have great relationships with each others family’s and we get along so well. I have been noticing that he was not acting as loving as usual. I would ask myself if it was me and if I could have been the problem. He wasn’t showing much effort and wasn’t posting me as much or even giving me reassurance when I needed him to. I would obviously talk to him and be like “Hey if you want to be with me I really need you to start showing me more effort” I really don’t ask for much but even picking a flower on his way to come see me or buying me my favorite snack at the gas station even when I said I didn’t want anything, little things like that. My love language is affection so I guess I expect the same in return. This last weekend I went on a mini vacation with my family. He was going out with his friends bc he turned 21 two weeks ago. I let him do his thing and don’t think much of it. (He’s been going out with them maybe 2 times a week.) I’m at work that next week and I get a message from a random girl saying “Hey I know you don’t know me but your boyfriend is cheating on you, you don’t have to believe me but I promise you I’m not lying, I can get you proof ” so obviously I didn’t want to believe her so I message her saying “oh wow. Yeahh if you have proof send it my way” so she starts telling me that her friend doesn’t feel comfortable telling me and that they didn’t have any actual screenshots bc they were using the app Snapchat but she told me that him and her friend ended up having sex. Keep in mind he is really the sweetest guy ever besides not really showing much emotion. So I’m like WHAT THE HELL IS HAPPENING. So going back to before this all went down, I’ve been with him the last couple of days and one night while we’re sleeping I notice some small scabs on his back, kind of like scratches.So in the moment I confront him about it but I honestly didn’t think much of it. He said those were probably from going off roading with his friends and that was enough for me to believe him. So coming back to me talking to this random girl. She tells me that they met up at about 1:30-3 in the morning and like I said before had sex. The girl had said that it was only a one time thing but that she didn’t know that he had a girlfriend. (And I get that because he rarely posts me on his Snapchat) anyways the friend tells me “She said she might have left some scratches on his back” and when I tell I almost fainted at work when I read that message. My heart dropped to my ass and I did not know what was going on. Still in disbelieve I told her that I would need to see some type of messages or anything at this point that really does show me he was talking to her. She kept telling me that she was begging the girl to just be a woman and message me but the girl did not want to. At this point I started asking her questions like “what time did they meet up?” “ what car was he in?” “what was he wearing?” “what tattoos does he have?” and she answered all of those questions accurately. At this point I’m off of work and he had asked me to go pick him up bc he was having issues with his car And so I do. I get to his house before him and I’m just waiting for him on his bed. I see him and tell him we need to talk. We’re on his bed and I start balling my eyes out. He asked me what was wrong and I just pull up the messages and he acted shocked. He was like why are people trying to break us up and I wasn’t with anyone bc I was with my friends and you know that I came straight home and all this and that. So I tell him that we will call the girl and see what she has to say. So her friend gives me her own number and I call her and then she called the other girl so we are in a three way call. The friend seems like a genuine person and starts off by saying “You need to tell her everything you told me. I know you don’t want to but you have to. You can’t be a coward and not come forward.” So the girl starts off by saying she’s really sorry and how she promises she didn’t know he had a girlfriend and this and that. She talked about how she added him and that she swiped up on one of his Snapchat stories and they began talking here and there. She said she would flirt and he would flirt back and at this point I’m just staring at him and looking at all his facial expressions. She then proceeds to tell me about the night they hung out that she sent him her location and that he had it saved in their messages and that they met up and ended up having sex. To be honest even after all that I still didn’t want to believe it. She explained to me via phone call how he was and his appearance and that she did possibly leave some scratches on his back and his hand tattoo. So at this point I just tell the girl thank you for telling me and hang up. I look over at him and tell him “what do you have to say about that” and he’s still denying and denying he tells me that it’s not true and if they don’t have any proof that why should I believe them. So I ask him if he even knew the girl and of course he said no. So I tell him to give me his phone and then I add the girl on his Snapchat and I get my phone and message her because come to find out i had her as a friend on there too. So I tell her to accept his request and I do see that in their messages there is the saved address. So I tell him “If you’ve never talked to her why is this address in here.” He said he doesn’t know. At this point I’m begging him to just tell me the truth and he says “okay fine she did message me, but that was it” so I got my stuff and started walking out towards my car. I tell him that why is he even lying to me and telling me he doesn’t even know who she is but then he admits to talking to her. I sit down in my car and he’s at my door. I start crying my eyes out and tell him “PLEASE PLEASE JUST TELL ME IF YOU DID” “I’m begging you PLEASE JUST TELL ME IF ITS TRUE” he keeps on saying it was not true. I knew that he really did love me and if it was true he would tell me because he has never been a liar. So I finally tell him “If you love me like you say you do you would just be honest with me and tell me” and I see a tear roll down his eyes and he looks down and says to me “I fucked up.” At this point I honestly wasn’t even mad. It was more of this sadness that just took over my body but I’m trying to play it cool. I tell him “So you did have sex with her” and he tells me again “I told you I fucked up. I’m sorry” I don’t say anything back. He tells me “I’m sorry. I didn’t mean for it to happen it just did.” I asked him if he was drunk and that’s why he did it because that was one of the nights that he was out with his friends. He tells me that he doesn’t want to say that it was because he was drunk because that was no excuse. He also tells me that this girl and him were only talking for a few days and that it just happened. So I tell him that this is it and I start driving home. I wasn’t even crying to be honest. I was shocked at the fact that the man that I thought was going to be the father to my kids one day could actually do that to me. When I tell you I could have bet 1 million dollars that i had found my person and that this was going to be who I would spend the rest of my life with i would. I was also thinking to myself that if this was even real life because he’s always been the sweetest boy and out of those 4 years nothing like this has ever happened and I trusted him with everything I had. So I guess that this is where the advice from you guys would really help me a lot. I love him so much that I really don’t want to be without him 😔 despite of him doing that like even when it was all going down I still wanted to give him a kiss goodbye and hug him and cry in his arms. I really do love him with all I have and I don’t see my life without him! He’s the person that I go to when life is treating me unfairly. He’s the person that when I’m arguing with my family always has my back. At the end of the day I feel safe being wrapped around his arms and his hugs give me comfort. Idon’t know if this sounds stupid of me but I have friends that have gotten cheated on and have broken up with their boyfriends several times and are still together. So I keep comparing that to us. His sister and her baby daddy have split up more than 4-5 times and had gone with other people and they are still together. Not saying that that’s right but something in me just wants him to stay even after HE was the one who fucked up. The girl even told me that he didn’t want to kiss her and that he wasn’t talking much so I guess it was just meaningless sex. And that they had only been talking for less than a week.But I still ask myself why. If he loved me like he said he did he would have never done that to me. All he keeps saying is I’m sorry and I’m sorry. Not once has he said “please I want you to be the girl in my life forever, I messed up and I know it but I want this to work someway somehow” and I guess I’m kind of just waiting for him to say that. I seriously don’t know what to do since I have never been in this position before. The girl told me that she thinks he really is sorry because he ended up taking her off again. But I really just don’t know. He said he wants to talk to me when he gets off of work and I am willing to listen. But if I don’t hear what I want to hear coming out of him, then I think I should just walk away right ? 😔