Long Cheating Story!! Advice Pls!!

edit!!!!: he hasnt messaged her since october with proof and since then has been back to himself no drugs some drinks but he has been loyal

so please dont judge me im begging. last year during september october my boyfriend spent a lot of his time drinking and doing pills. he had this one friend who did not like and that where he got it from. during that time he was a different person and i knew something was off. there was this girl that i never liked and she started working at my boyfriends job. now i usually dont do this but i told him dont talk to her or add her on anything. in september on my birthday he was cuddling me and he was on his phone and i woke up and seen it and i asked who it was, he said his friend hunter but i seen the name. they had a 7 day streak. he unadded her and we went w our day. a couple months later this one friend of mine told me he seen the girl texting my bf and they were talking abt having sex and all this. i confronted my boyfriend and i cant really remember what happened then.

but the same night my bfs friend friend told me what my boyfriend has been doing. this all happened in october and i found out abt it probs a month later. he told me they have been talking and they kissed at work. i flipped out on my bf and he came to my house and explained to me that she kissed him and that it didnt mean anything and he only kept talking to her bc he didnt want her to tell me that he kissed her. i forgave him. a couple months later hes texting someone one his phone and i peep that theres two of the same names in his phone. and i ask did he get a new phone number? he said no and must have forgotten that it was not that actual person, it was the girl. right away i see heart and take the phone and he freaks out. i see everything. those text were still from october and it was probs like december when i seen them but the things i saw were news to me. the main thing i saw was him complimenting her and he took me to work EARLLY TO HANG OUT WITH HER!!!! was i wrong to get mad even tho it was months later??

so im currently still with him he has apologized forever and so much and he admitted his wrongs and made it up to me he blocked her on everything. drinking and drugs arent an excuse but i think if he wasnt doing that he wouldnt have done it maybe? but anyways its now many months later and i still overthink about everything and im scared hes always going to cheat and sometimes i don't believe him and he gets upset about that. hes very caring and ik hes still very sorry about it but idk how to get it out of my head and just stop overthinking. pleaseplease let me know your thoughts or what you have done. im so upset with myself but idk if i should have left or not. one thing is i wish that when i found out about it at first that he wouldve told me the honest truth, he gave me his phone to look thru but i was dumb and didnt and then that turned into me finding out more stuff a month later. im just a little lost on how to fix my trust issues with him...