TTC but feeling sad

My husband says he wants another baby but when it comes down to it I don't think that he really does.  I'm 34 and he's 35 almost 36. At first I wasn't to excited with the idea at first because I had so much trouble with my first and second pregnancies and have had two cesareans. But I said ok. I told him if we were going to do this there was a limit on the window of opportunity because I don't want to have children after I turn a certain age because even more problems can arise. Our sex life isn't that great but now it's getting worse. When I say to him I'm ovulating and this is a good window of opportunity he acts like he isn't in the mood. And flat out rejects any advances I make towards him. Now my feelings are hurt and I just want to give up at this point. We already have a beautiful 5 yr. old daughter and I have a gorgeous 16 yr old daughter from a previous relationship. I think it's time I give up and just focus on the two I already have. Any advice??