I need to vent

My boyfriend wants to do something that makes me uncomfortable. He's going to sleep over at a friends but there will be other girls there. We're long distance so there's no way I can be there. I feel so anxious and uncomfortable with this. It's not like it's just him, I wouldn't really be okay with this with anyone I was dating, I just feel weird and it would make me anxious. There's been this pattern of him pushing what makes me anxious to the side so he can do what he wants and I really want to put it to a stop and stand my ground, but I don't want to lose him. I'm not telling him to not go, but sleeping over there gives me a lot of anxiety. If he does go through with it I don't know what I'm going to do.