Complicated Mess

We started dating after an awkward situation that we eventually got past. From that point on there entire thing was a whirlwind, with complicated situations, that do not pertain to all of this. At first the love making was often and then one day he said, we're making love too much. I was in shock, a male saying it's too much! I was hurt and confused and I told him so, we talked about it and eventually came to an agreement. Then this past June, he had a week off work, he was taking it off the take care of some things for our son and spend time with him, or so I thought. The following week, I did not have to be at work until 11 so I was spending sometime working on the wedding plans, when I stumbled upon what he had really been up too...Porn. I decided that I would confront him about the issue and see what he had to say. At first he would not talk about it, he was instantly mad that I would even think that. At that point I got very sarcastic with him and said, " Okay, if it was not me or our son, OH! I'm sorry it must have been the Cat." At that point he realized he was busted and started talking about why he was looking at it and how long it has been going on. He stated that since as a young man his parents were very strict and would not allow him to go out, he had to find ways to take care of himself. He has relied on this for years, from approx 16 to now 29. I told him that it made me feel very low and that I did not appreciate it. I told him given the fact that I had been extremly open with him in the beginning of the relationship, in terms of watching porn while making love to spice things up. He said he was not interested in any of that, it wasn't his thing. Now all the sudden he's watching it while I'm home but sleeping. I told him that he had to cut it out or I was done. He stated that he would stop and that he was done and I was the only one that he wanted/needed to see naked. At this point as far as I know he's been honest with me and is not watching or looking at it anymore. I cannot seem to get it out of my head, I think about it day in and day out, what if he hides it again. How can I get him to understand how hard it is for me to believe that he's done with it without him getting upset?