Is it really JUST the sex that might doom the relationship? It really doesn't seem to me that this could be happening in a vacuum. And, after all, you guys have had your troubles before, since you've had so many ups and downs in the relationships. There's more to it than just sex.
Honestly, it sounds like communication isn't there, and that's a foundation of a healthy relationship. Not to mention something with the desire.
Sex shouldn't be a job you're required to do. If someone bitched about not getting sex enough, they'd be out of my life so fast. Because sex is about sharing and both loving it. Just because you're together does NOT mean you have to serve him. (I have major major disdain for people with a sense of entitlement, as it sounds he does.) Yes, sex should be a give and take in a relationship, but it should never be something someone should feel any pressure to do if they aren't comfortable or enjoying it.
I'm pretty much with everyone else. Anyone who demands sex of me would be out the door. Anyone who did anything as hurtful as rolling his eyes when we were having sex would be out the door.
I've been in the relationship I've been in for nine years, almost as long as you've been with him, and things are wonderful and happy. It's not really that long! If things are this crappy already, I'd be seriously thinking about getting out of that situation.