Hi Lee,
I think you should tell her that the reason you do not want to take up with someone else is that sex is not just a physical act for you, that it means so much more. You would be forming an emotional bond with someone else, and that in your heart you want the intimacy to be with her. Assure her that you want to work on it a step at a time( the idea of being a sexual person is overwhelming for her now) with the goal to be closer with her, not for hot sex. Let her know you don't want to give up on your love for each other.
J -- who knows it's not easy