I should be okay with this?

OK, so this is a major bitch session. Today has been horrible. Family problems mixed with a little relationship issue...what else can possibly go wrong? Bobby just informed me that he's going over to Joey's apartment to drink. The catch is, the girl he hooked up with while we were broken up is going to be there more likely than not. I mentioned to him that I really hoped he wouldn't stay there if she was there, and he told me that I should let him have fun and I should trust him...the thing is, it really hurts me to think that they'll be hanging out together and drinking. It feels like somebody is punching my chest...I want to cry. I told him that when he wanted me back that I would not be ok with them hanging out, and he was like yes, I understand...clearly, that was just a stupid excuse to get me back. Now, he says that I should trust him and let him have fun....what, fun is hanging out with her and making me miserable? I even invited him over here to watch a movie and sleep over...but, that is probably the last thing he would ever want to do. UGH sometimes I wish I were single. It's like, am I supposed to be okay with him drinking and hanging out with her? I don't hate her...I just feel extremely threatened by her. Ok, so I think I'm going to talk this over with Mom...ciao.