Why does my husband only want to have sex when he initiates it & not when I want to?

Hi. My husband and I have been happily married for 10 years and together for 11 years. There is a 10 year age difference between us, but that's nothing. Our sex life at first was like most...ALL THE TIME & intense. We have had our problems through the years but our marriage has become stronger through it all. I guess my only complaint would be that he mentions his ex wives and their past with him at least every other week, and has never had a problem with talking about his sexual escapades of his youth. It has become so annoying over the years. I don't want to talk about his ex wives at all and I definitely don't want to talk about his past sexual escapades. I try to make him see that when he talks about it...that i'm dong everything I can to change the subject and ignore it. He mostly never catches the hint though. I usually just walk off or act like I have to go do something really quick. Does he still care about them? Also, there have been times when he chose pornography over me. That was a big issue at one time that I thought we had settled. I had even gone so far as to purchase or watch with him, just to please him or make him want to. We fought with that issue for 3 years until I gave him a choice a year ago. He didn't do anything for a whole year, until recently. I found a website in his history where he can look art, but it also has what looks like to me porn pics of women that pose, completely exposed and in sexual positions. I even saw him looking at them one night...then he came and initiated sex with me. If I initiate sex with him though, he's either to tired, stressed out or "isn't in the mood". I'm left feeling like WTF? I have needs too & I want to have sex when I want to as well...not just when he wants to. He also makes me feel guilty for asking when I want it, by getting mad when I tell him how I feel. I don't think it's fair for him to use sex with me as weapon (which is what I think he is doing), and I've been left feeling confused over the years..but have gotten used to it, but I still want to solve the problems. Any advice? Thanks