Found my boyfriend talking about another girl what’s should I do moving forward!

I F(20) and My boyfriend M(21) have been dating since I was 16….I know. And we haven’t necessarily had the best track record we have broken up two times the one that matter was during college my freshman year it was extremely messy and we were pretty toxic and we didn’t see each other for 6 months and we’re no contact I was seeing someone else during that time and I think he did too and just doesn’t want to admit it to me. He doesn’t know how to communicate great or doesn’t show much emotion or empathy and he definitely struggles when it comes to having to apologize to me but he tries very hard we got back together and have been together since and we’re now juniors and seniors in college I truly thought he had changed since then and was becoming a better person he seemed like he cared about changing and cared about my feelings when he hurt then it just felt like we were so in love again and not like the other times where he super irritated or just always angry…but today I had a really bad intuition feeling and pit of anxiety in my stomach (I know I sound crazy) about him doing something weird behind my back I had even dreamt about him talking to this girl from the past (a girl he claimed he didn’t like during our first brea up our senior year of high school but I knew deep down he did like her) So while he was sleeping in my dorm I searched through his phone. I found nothing at all I felt relieved but not satisfied. So I went to his iMessages and typed her name in the search bar and found her name a month ago he messaged his friend saying he saw her again while he was out and that his “heart dropped” and that he think he still has a “big fat crush” on her after seeing her and that “it was crazy of him to say this because he has a girl”(me) now my stomach immediately started to hurt and I didn’t know what to do because I was more sad that I wasn’t disappointed by his behavior I woke him up and told him about it and I can tell he felt very awkward and embarrassed but he was so stand off ish he immediately told me that it wasn’t true and he didn’t like her and kept denying it and his explanation was that when he said he had a big fat crush on her that it was “OD” and he was doing to much because he just felt shocked he never admitted that he liked her before and would just deny it but he told me that when we were broken up in high school he thought she was pretty and since they sat next to each other he did like her but they never talked. But that when he saw her he just remembered his past feelings towards her but that he doesn’t feel that way. He then told me the normal I only like you and love you and want to be with you. He did comfort me and tried to apologize and reassure me that he doesn’t feel that way about her and that he was just reminded of old feelings towards her when he saw her. Now I know that finding someone else attractive is just human nature but it hurt me so badly because I do not do things like this I don’t mention liking anyone else I’m extremely respectful and he was a track record of doing things like this. I have never been insecure about any other girl but this one she’s extremely pretty nice and cool. So am I but see him say that made me feel less than. He mentioned how he only wants to be with me so he is and that she doesn’t mean anything to him and it was just a small crush from the past. They never talked or even dated they only even talked for homework and in class that I am 1000% certain of so it wasn’t even a talking stage and they never dated so I just I feel so horrible I feel like shit and like I’m less than her and I don’t know what to do. Is this worth breaking up over or can I fix this? If I stay with him will I just end up resenting him? Or Am I just being overdramatic and it’s not a big deal that he used to have a crush on her I’ve had crushes on people while we were broken up. I love him so much as embarrassing as it sounds I’m not sure how to leave him we’ve been together for so long what should I Even tell him going forward because I told him I have to think about what I want to do moving forward. I feel so embarrassed for myself and keep beating myself over acting like I have no self respect. Please anyone give me advice.

TL;DR; : I found messages in my boyfriends m(21) phone where he said seeing a girl from his past made his heart drop out of shock and that seeing her made him think he still has a big fat crush on her. He then told me that he was just shocked while sending those messages and didn’t actually mean it that way that when he saw he he was just shocked and was reminded of those old feelings And I’m not sure what to do and if this is worth breaking up over.