Need help...

Background: My boyfriend and I started snapping each other constantly (i actually got snapchat because he asked me to) at the end of the  last school year, we dated for about 2 and a half days. Then he broke up with me without any explanation and immediately started dating some other girl call her girl A. I don't know how long that relationship lasted seeing as school had ended. We went the whole summer without any contact. At the beginning of the next school year we ended up sitting near eachother due to the fact that we got to choose our seats and we have a mutual friend. I had gotten rid of snapchat on my current phone but left it on my old phone which I don't have anymore but I decided to open it one day and saw that he had been trying to talk to me. I hesitantly repied and we started talking again. We started dating again around the time we had our homecoming. A few days later I got told that he kissed this other girl (who gets around a lot) but he assured that she had initiated the kiss and he didnt kiss back. I let that go however since we have been dating there have been rumors that he has asked someone to have sex with him (there was another incident in which she had tried to get together with him but he said no and told her he only liked her as a friend)and has had sex with girl A (girl A started the rumors).

The problem: On Saturday I saw that my boyfriend had a snap from a girl. I brought it up later and apparently it's an EX he has and according to him she started talking to him because she found out that he has thought of killing himself because he has dated a few people who have all cheated on him. In front of me he grabbed his phone saw the notification and said 'no thanks'. Later that night however I saw that he had snapped her back, that really bothered me because he said he didnt want to talk to her but did anyways. He then removed her as a friend because it seemed to have bothered me. On Monday I went over and turned his phone on to check the time, I  saw that girl A had sent him a message and he told me to tell her to fuck off. After doing that I got out of the chat and saw that he had an 3 day streak with  his EX after telling me he wanted nothing  to do with her Saturday. I asked him about this and he got really mad because I have a streak with a guy friend. He said it was no different, knowing that my guy friend and I dont actually talk it mostly blank snaps. He then said that he wanted no drama and deleted all his social media including snapchat. Not even an hour later he had snapchat again. I had glanced at his number of snaps and he had around 17,090. I got curious this morning and I saw that it had raised to 17,144. Throughout the day his snap number has been rising and when I asked him who he was talking to he claimed it was a guy named tyler and quickly showed me his phone and then turned it away. I saw the name and it said javi (a friend he no longer talks to). I didn't saw anything because I was close to crying and we were in a classroom with a lot people. I just saw his snap number and it is now at 17,263, I have a feeling he has been snapping his EX. I tried talking to him but he'll start talking about how he feels like a terrible boyfriend and then I'll feel guilty and let the subject be. He has told me that he wouldn't cheat on me but I still have my doubts seeing as he's talking to his EX and he seems to be hiding his phone when im near. I'm not sure what to think anymore, maybe someone on here can help. I hope this makes sense.