Not Married Yet. Fiance Won't Admit Addiction 2 Porn

I know this topic is just about everywhere on the net and I know I can go to any of those sites, even earlier ones here, and read, but I kinda feel that this is alittle different. Therefore requests a new topic to answer to..

Without going into to much of our past. We have had an amazing relationship from the very beginning, but I was not as "clued into" his obsession with porn. We then had a son. One night I found out that yes, he views porn and yep, I was mad and cried.. etc. He stated to me that he was ashamed and will "try to stop". I believed him until I found him doing it again and again (checking the computer log). My fear is, as we are not married, that I will one day just "give up" and head out the door, but the man I love is an amazing father and I can't pull his son away from him (I never would). Plus, in my head, then I just let go our family, of him and left him to his porn addiction-which won. I will not do that! So, we have talked so extensively about this subject so so many times that I now thinking I may just have to live with this as is, but I can't do that either. I am trapped and yes, I watch porn, but only with him (as I thought foolishly that was what we were doing). I caught him just last week watching a video of young girls out on the beach and yes, it made me very very angry and yes, I felt betrayed and lied to. So, we had yet another talk. I just don't want anything as silly as porn to get the better of my family, but it erks me so darn much that I feel it's winning and in the end I will walk away. I would absolutely dislike my son coming home to me screaming at his dad because of his obsession or wake up to me crying and he ask "what's wrong mommy?" and then I actually, in anger, tell him "your father is a .... " And so on, because I will be so so mad. So, I need some advice.

Porn is not unhealthy, but the addiction is. I have to ask myself if what I am doing is fair to him? See, this last time, I caught him in the room watching that video and told him that he has to decide... (yep the old ultimatum). Was the right of me?

I read that it is only unhealthy because it hurts someone close to them. Well, that someone is me, at the moment. During our talk he promised to quit, but yet has never admitted that it is an "addiction" and never once sad "he was sorry". To say sorry is for him to own up to it, but he will not.

I have to believe that he will try to quit, yet in the past, he failed. For now, I am asking him probably every week if he has viewed porn at all and that he can tell me without me getting angry, as I just need him to be honest with me. So far, I can't say that I believe him, but he knows that I too am trying to overcome this and we are working at it. I guess my question is.. Am I wrong to ask him to stop? If this was what he was before I knew him?