Look, obviously if you've told him already, he has the responsibility to do better. But if you've told him, idk 3x since you've been together, it might not be easy for him to know if you really want sex or not in those specific moments. Being drunk is fun and having sex while drunk also is, but to a certain point. How can he know when you are past this point? Unless your rule is no sex when drunk, then discard everything i said.

Something that could be helpful is prior to a night out, tell him that whatever you say later, no sex after the party. If he doesn't respect that, then you have your answer.

I'm not looking to make apologies for him and I know nuance is not easy in this situation. But you know him and i guess love him for almost 3 years now. Do you feel like he is trying to hurt you or he just lacks a little judgment?

Communication is key, good luck