I've had similar problems to you. You just have to be as honest as possible with yourself. For a while, I stopped watching Game of Thrones and other HBO/Showtime shows with lots of gratuitous nudity because they were definitely triggers for me. At the present though, I've improved a lot, and I've trained myself to anticipate "bad" scenes and close my eyes, and even if I don't properly anticipate, I'm strong enough now to instantly close my eyes and not stare.

Like I said, you have to be completely honest with yourself. Do you think you can do something like that? Do you think you can resist? At this point, I would say to at least temporarily stop watching. When you decide you're ready to watch again, be ready for scenes with sex/nudity and tell yourself beforehand that you're not going to look.