WHY doesn't he care at all? Why do I care if he cares?

My husband and I have been married for almost 15 years and together for 18. Since I was was 15. We have two children. Twelve and eight. He did cheat on me with his ex-wife right after we were married and yes, I know how stupid I was to stay but I was 18 and pregnant, had been married for two wks. and was totally devastated and stupid. Hind sight is 20/20. He honestly did change. It took a lot of heartache on my part and stupidity/ignorance on his but he did. He is a good dad and provider. This is the problem...when we were young, before and after we were married he talked down to me, told me he didn't care, basically treated me like crap. I had a very low self-esteem. For the past 10 years though things have been fine but it seems like things are steadily going down-hill. I don't think that he is cheating, really. But, I don't think that he cares for me in any way. He just has that same "attitude" toward me that he used to have. He hasn't said anything horrible to me like he used to but I can tell that he couldn't care less if I took another breath. I am so LONELY! I have never really known anything other than being with him. A part of me loves him but another big part hates him with complete pion. I think a big part of the reason I have stayed is for our kids and another for the fact that I don't really have anywhere else to go. Yes, I do have friends but they are married and have kids and have their own messed up lives to deal with. They sure don't need my drama. I have asked him in the past about going to counseling but I may as well have been talking to the wind. I just don't know what to do anymore. I feel so empty and alone. Don't get me wrong, I am blessed to have my children and I love them with all my being but there is a whole other part of me that is just empty. Sorry this was so long and believe me I didn't even touch the surface. I think I just needed to get some of it out.