I need support & someone to talk to.

I've been with my boyfriend for 3 years. We were always happy. I was 16 at the time when we started dating & he was turning 20 I believe or 21. I'm not 19 & he's now 24. Everyone makes mistakes little mistakes throughout the relationship. Whether it's saying something wrong or you know. Relationships will always have its ups & downs but I'm really confused right now & I know what most of you are probably going to say is "follow your heart" probably or something like that. I'm in love with my boyfriend but there's just a problem. He's been hiding things from me from the beginning we started dating. I don't think cheating is JUST sex & kissing & talking to someone else. I think cheating is also SEXTING, sending nudes, talking sexually to someone else who isn't you. The first time I found out it started with my boyfriend calling other women on Instagram "beautiful" "mine" "my love", also one day I saw a comment where he was saying to some other girl "call me after work my love". After all of that I started being nosey. I once checked his Facebook randomly while he was with me. I didn't ask for the password the page was already opened on his browser on his phone. I looked through it & I saw a bunch of girls he spoke to. A couple of "nudes" girls weren't completely nude but they have bras & panties on & he sent one with his boxers on & shirt off. I saw one where he asked the girl to go on a date basically on a Friday. A bunch of sexting. All of these messages happend within our relationship. I found out about all of that last year. 2016. I then gave him another chance. I worked with him at a job & I once found out a girl texted him while he was pumping gas into the car & me being nosey I looked & asked who it was & it was a girl who worked at out job as a team member for the hotel team. She said they spoke & I acted as him to get some information & she showed me all the screenshots & he was telling her that he was going to pick her up & asking her what she was going to do to him & stuff like that. I gave him another chance. Other things have happened where he would say i love you to another girl & shit. Let's just say things have happend many times throughout our relationship & I have given too many chances. I told him that this was the last straw if he were to ever do something like that again. Everything was fine for a couple of months until he started a new job. He worked with real estate agents. There was this one lady where it started off a conversation & I never trusted my boyfriend with talking to girls or even having girls as friends because of what has happened. Well let's just say some night around 10:30pm it ended up being a conversation for 2 hours straight on Whatsapp. I confront him about it & he says "no babe, we were just talking about real estate" i was like "Noone talks about real estate at 10 at night for 2 straight hours" he kept saying the same thing " it was about real estate" until I texted her acting like it was him & asked what the conversation was about & what we spoke about last night & she says "I don't have time for this" & never replied back. Tell me that's not shady. So I let it go. 4 days ago a situation happened where I was at work & I saw a dm from his account since I have his shit & I took a look at it & it said "why did you block me I just asked, I'm not gonna eat you" & I also saw the text message where the person sent to him saying something & my bf says "don't text me or text me through instagram please" because my boyfriend knew I had his shit & I was going to see it if they had a convo. I knew the truth & what was going on so I confront him & he says "no no no" & I'm like you better tell me the truth. I was dealing with this shit for an hour until 2 hours later he tells me the truth that he was speaking to that person & he was scared to tell me the truth because he didn't want to lose me & blah blah blah.. I'm in love with him but I no longer want to put up with this shit. I know in the long run it's going to happen again no doubt! But it seems SO HARD to let him go. Lady's I need your help. I'm sorry this was so long but I'm in need of girlfriends right now 😓