This poster mentions computer p 0 r n and I wanted to point out just computer abuse period.
I have just come from a relationship very similar to what the original poster has described - we are 31/32 years old and my b/f just didn't want sex, at all. Very infrequently anyway. I would have to do all of the pursuing, sexy lingerie would get him aroused but I would have to dress up and parade around, give him a lap dance or something. I'm not a prude but I'm no exotic dancer either and I just wanted normal sexual activity, not to have to "put on a show" every time I wanted sex - I really just wanted to feel wanted.
Now, the one thing I haven't told you is that he played computer games, like role-playing type games, War Craft or War World or something like that, was his game of choice but it could be anything. He would eat behind his computer and watch TV behind his computer, he often didn't come to bed until very late when I was already asleep - there was no time for natural intimacy. He had so much virtual stimulation (non-sexual) that there was no room left for sexual stimulation. At least that is my theory.
I have left this relationship - could the original poster have a similar issue? Maybe not computer related, but could it be work, or another type of hobby that keeps him so absorbed he simply doesn't have mental time for sex-play?