hes not my boyfriend

so i like love this guy and im not just being super dramatic yaknow weve beenon and off and talkin for about 2 years and i really do love him but we always break up and make up and make mistakes and ive never doubted his feeling but im not so sure now. so we broke up and he went to MY friends house party while i was outta town bur the whole time hes tellin me he misses me and us and all that its the usual. well he got drunk and slept wirh my close friend. i dont fin out till sje calls me on my birthday, while im outta town dealim with family issues to say "shes upset and heartbroken and possibly pregnant with his baby". im tryna be level headed right. but then she ask me to come over and sleep in the same bed she fucked him in and help her "through this difficult time" i was trippin. okay. it was my freakin birthday. i call him and he tells me hes sorry he was drunk he didnt even wanna have to stay there that night but he couldnt get back to his house because his car broke down. im like okay its okay . then they are dating. im trippin hard. he calls me later after they break up to tell me how sorry he is amd how its always been me ans whatever. then he tells me. hers thw shocker. he slept with my ex bestfriend. so like how does he do this cause the stuff he says to me is intimate. how can he say that to someone else. like are we just young and this is normal or is he screw in with me just bc he can.