I have 3 or four buddies who regularly cheat on their girlfriends / wives. Their standard M O is to accuse the girl of cheating. If you haven't had sex in three weeks or so, I think there is a real possibility he has gone elsewhere.
I don't tell you this to injure your pride, etc., I am trying to give you a guy's perspective.
I know this post will generate a flurry of responses about things that women wish were true but aren't.
Take care of yourself - you should be your first concern.