How do you deal with your man leaving you for an older woman?

My boyfriend and I have been together for a little over 2 years. I found out about 6 months ago that he was seeing a woman 10 years his senior, we are 27, and it literally destroyed me. He promised it was over and that we would work it out. Then I found out on Valentine's Day when she called me, that she is still seeing him. To say I was crushed would say the least. I am not only dealing with issues of infideliety, but the fact that he left me for a woman 10 years older than me. It has made me question my worth as a woman, and I have NEVER been in a relationship where this has ever been an issue. We have just started back having civil conversation with each other and he keeps telling me that he doesn't love her like that. She has sickle cell and is constantly sick, so he says. I think she has figured out that he is still communicating with me, and just using her sickness to her advantage. What do you do when you love someone who doesn't know if they love you or someone else