My girl is tired of ...?

So here is a little about us. Me and her were best friends for years before we dated. I stood by her side and helped her through an abusive relationship with her ex. After they broke up we both admitted our feelings and took it from there. We have had our fair share of bumps in the road, but over all its a great relationship. Recently she has been acting really weird. We used to be very ually active with one another but recently that's starting to fade. She never initiates it anymore, and when I do I feel like she's not even there. We will be having and she is paying more attention to the tv than she is to me. She told me that she just doesn't like anymore. She likes it bcs I do but no other reason. Im confused bcs I know how much she used to love having with me. She said she likes having s but the actual act of just isn't fun anymore. And it has been harder and harder to even get her to have one. I feel like im not good enough or its something im doing wrong. It is going a lot farther than just that too. Our relationship as a whole has been dying for a month or so. I can't sleep at night bcs of it. She said she used to like bcs she couldn't get it bcs her last bf that she actually lost her virginity too wouldn't have sex bcs he believed it was wrong. Now she's with me and I give her all the sex she wants so she says its just not exiting anymore. I feel like maybe she regrets its with me and maybe misses him. I don't know. Iv thought of maybe just saying no more sex and waiting for her to make the move. But she just wont. Im confused and hurt and really need advice. Thanks for any u might have.