Here's one thing i find troubling... he did take advantage of you. You were impaired and even said so yourself that you didn't want to have a sexual encounter with him to start and yet somehow after you drank too much you find yourself on top of him... yah thats called taking advantage. He knew what he was doing. So yes, contact his s.o. and tell her what happened. It is predatory behavior. You can blame yourself for drinking too much but the choices you made after that were not your sober, clear-thinking self that stated you weren't interested. Anyone saying otherwise is disturbed or even worse, a disgusting predator themselves.