Fuck boy/love of my life 😔

Maria • 19 years old👑 02/18/17💍 🇲🇽
Okay so I met this guy in January of last year, he was new to our school and just was completely different from all the other guys. 
Which I liked, we talked and got to know each other and of course I just fell in love with everything about him. We started dating that February. After the summer he broke up with me for no absolute reason. He didn't give me a reason why. He wouldn't give me one and it hurt me so bad because I really really love him a lot. A couple days after the break up I find out that he was in a closet with another girl at school. How on earth did they not get caught? I have no idea. When I heard about it I felt completely used and I cried all day. At lunch I went up to him and asked if it was true with some of my friends, and he didn't even deny it. He just kept apologizing to me and what made it worse is that he didn't even have the guts to actually tell the straight up that he did it. He looked ashamed, and sounded like he knew he was wrong for doing it. About a month later we had homecoming and I went with my best guy friend. And he asked the girl he was in a closet with to the dance. I told myself to get an awesome dress, get my hair done, do everything I could to make him notice me. It was so hard for me to even be there knowing they were together and that they could be doing everything under the sun without me knowing or seeing. After being at the dance for only like 45 minutes, I had to leave because my anxiety took over and I couldn't function right thinking so much about him and her.. Later that night I poured my heart out to him and he sounded as if he felt bad but it just hurt so much to know that he didn't  care enough to maybe realize what he was putting me through. Like I would be crying my eyes out and he still didn't really care. After the dance he talked to me and tried to explain but he wasn't making any sense and when I would ask him something he wouldn't answer my question. But I decided to completely shut him out for a while because he made my emotional and mental health go out of whack. I had to go to the hospital from panic attacks at school from even being near him. Those couple months sucked ass. My grades went down also. So basically what he did turned my life upside down. 
After a while he came to me and told me that what he did was a mistake and apologized about everything he did and like the stupid girl I am I told him it was okay and that not to worry about it. He ended up asking me out again and I said yes because again like I said I was stupid in love. 
We've been together for 5 months. Everything's okay but every now and then I go through this thing where I think about what he did to me and it makes me so depressed, when I think about it it'll usually because I see the other girl around school, or I see something that reminds me of what happened. I think about how I felt and how it effected me in such a negative way nobody's ever made me feel before. 
I think about how I would ask myself what was wrong with me and why he did what he did, and maybe it was my fault that it happened and how I would compare myself to this other girl who was a bigger girl and was kind of like the school hoe. 
And I'm 16, and I'm like 4'10 so I would always try to figure out why he wanted her instead of me. I didn't feel good enough for him. I felt like I had to step out of my comfort zone in order to grab his attention. Because the girl he liked was always having sex, always taking nudes, always into terrible stuff. And me, I'm just really shy, and not that outgoing and I'm not the kind of girl to just go out and do that stuff to get guys to want me. I hadn't had my first kiss until I got back with him because I felt pressured into doing it because of her and I didn't want him leaving me again. 
I still do this day think about what happened and just sit in my room and cry about it for hours at a time. I'll cry about it in front of him and he'll start to cry too. Which makes me think he really does regret what he did but it keeps running through my mind all the time. And it's not healthy for me to think about it that much. But I do anyways. 
I'm not sure if I should've given him another chance or not due to all the stuff I went through and is still going through but he's different now. He apologizes at the most random times and cries about it a lot. I just don't know what to do. Should I stay with him?