What's up with that?

[Wondering]

My boyfriend/fiancee have been together for close to 3 years. We got this computer and got online at the end of August. At the end of September I happend across an email that he thought he had completely deleted, he had not. The email was a confirmation of his registration to an adult friend finding site. I dug into it and found out that he was looking for someone in our area to have a discreet, non commited, sexual relationship with. That wasn't all I ended up finding either, I found hundreds and hundreds of porn sites that he had been visiting since the very first day we got online. Now I don't really have a problem with porn, since I was an exotic dancer for the last 7 years. I have a problem with the fact that the man I love, seems to have lost all sexual intrest in me, we haven't had sex more than a couple of times a month, since March, and I am the one to initiate it 95% of the time. What is up with that? Does he really find pictures of other women more interesting than the real thing, or is it just that he is tired of me? And his looking for someone else to have sex with just blows me away, I have no idea what to do or what to think, can someone please offer me an outside point of view!