Boyfriend problems.

My boyfriend and I live together. He always wants to go out but without me. He's had sex with the girls, they're very pretty, and he is going to be drinking and he is so flirty with people when he drinks, he is going with the girls and specifically tells me not to go even if I am invited. His friend he is going with is a bad influence on him and always causes so many problems. They've slept with the same girls and take great pride in that and the friend doesn't care for me because I don't drink and I don't party because I am in college. I love my boyfriend so much but it feels like I am nothing to him. He says he doesn't have fun with me but plans to marry me and wants to stay with me. I need advice of where to go from here. Should I try and work it out. My heart is just hurt. It's breaking. ?