What does it mean when my ex husband only wants sex from me?

We were in a relationship for 12 years, married for 4 and I left him because of his drinking. I wanted him to realize that he had a good woman. I packed and left with the kids. None of which are his and he was mad that I just left with no notice. Then he moved out of our house and in with his sister. He says that he loves sex with me and that he still finds me attractive although I don't feel that way right now. He filed for divorce 2 months after I left, I signed the papers and sent them back. But I miss him like crazy I never thought he would have filed for divorce. He tells me that he is still very attracted to me and that he will always be there for me but he can't be in a relationship with me. He is worried that I will sleep with someone else, but assures me that he isn't looking to sleep with anyone but me I don't believe him. Is there hope?