Replying to Your opinion on the situation

My boyfriend sleep talks about this girl he fucked last year. All the time. It wasn't too big of a deal, because she lived in Australia. Now she's moved back to the U.S and of course, the town my boy and I live in. And he's "so excited" that she's back. She's having a birthday this Friday, and of course he's going and I'm expected to come with. I don't want to fucking go, but I feel like I have to because I don't trust either one of them. I really like this guy a lot, but im wondering if i should just break up with him and avoid the shit storm that's going to follow. Or do I give him a chance. Opinions?