I am just reading a lot of self-pity here.. and it's all over nothing. Her past has nothing to do with you. Nope, not ever. Just as yours has nothing to do with her. If you can't get over her past, then as the other said, leave her. I don't completely think this is the issue tho, as you've admitted you forget about it until you don't have sex for a while. Why is that?

And sex.. she doesn't have to do one single thing that she doesn't want to, and she doesn't owe you anything or be made to feel obliged. How about moaning less, less demanding this that and the other, and perhaps giving her some space to breathe, romance her and she may, just may feel like pleasing you more. Nothing is a promise, but you'll probably have a better luck with kindness than whinging. Sorry.