Babymama drama!!! i neeeeeeeeeeed help!?

i recently started dating my bestfriends, boyfriends, bestfriend.. i know confusing lol .. and everything was going excellent until his babys mother started all this drama because he had a new girlfriend and because she wanted him back. After about a 2 weeks, he broke up with me. He said he was confused and didnt know what to do, he said he knew he had to make a choice between her or me. At first i was sure he was going to pick her but he told his bestfriend, which is my bestfriends boyfriend that he realized that his babys mother wanted to be with him for all the wrong reasons, and because she didnt want him to be with anyone else.(mind you, shes living with her boyfriend who she just broke up with to be with her babys father.) to make a long story a little shorter, he said he decided to work things out with me and him until the next day when he started talking to her again. After that we all went to my friends house to spend the night, except his babys mother, she wasnt there, duh. So all that night and the next day hes huggin me and kissing me and then he leaves but not before he gave me one last kiss which in my book i thought meant, ok so he wants to be with me, only to find out 2 days later, hes back with his babys mother. She starts alot of drama for no reason and wont even let him come chill with us no more unless shes there and honestly that would make me feel VERY uncomfortable. In like 2 weeks my bf's boyfriend is havin a bday party and inviting both of them, i dont know how to act when i see them, i wanna chill but its going to hurt watching then kiss and be together because honestly thats who i want to be with. please help me. how can i just forget about himmmm?