My ex still says he loves me and says he wants to be with me but why does he stay with someone else?

My ex cheated on me when we were married and got the other person pregnant. After years apart we got back together and everything was good we had another child were going to get remarried. We started to have some problems with jobs and he cheated on me again. But, when I do see him he tells me that he still loves me and still wants to be with me and our kids but he has alot of things going on in his head. And than we end up sleeping together this is the same thing that happened the last time that he cheated on me he lived with someone else but still slept with me and told me the same thing as he is telling me now. I love him with all my heart and soul and want to raise our kids with him but I don't know what to believe anymore. Does he love me? Or is it just another lie? I am so torn