I think in this digital age we live in now, that most men and woman have probably at least seen porn at some time or another and lots of us have watched it a few times, some watch ir regularily.
The reason for men to watch porn is to get turned on yes, but mens brains work differently from womens in that men tend to lean more towards visual stimulation, where as women tend to prefer the fantasy and the feelings involved. I think this is why the stats are generally higher for males watching porn than females.
However, it does not mean he thinks less of you, or fancies you less. My guy used to watch porn before he moved in with me and to be honest, I would not be bothered at all if he watched it now, but he doesn't. I watch it much more often than him (Which is how I know he definitely doesn't, because he has no reason to lie to me, considering we are pretty open and I watch it myself)
Anyway, from what he said, men watch porn kinda like why we use vibrators...its an extra boost to them from to orgasm quicker. They don't always tend to fancy the women in porn, but are just watching porn to see the actual sex acts. They will often then imagine that they are doing what is on screen with their partner, or just simply get off on watching, without thinking about anything. As soon as they orgasm, the interest in what they are watching is completely lost and it gets turned off and totally forgotten about until next time they are horny.
Porn, for men, (and some women, like me and others who have commented already) is basically the equivilent of us females reading an erotic story or having a naughty fantasy. It has absolutely no bearing on you, or how much he loves and fancies you. None at all. It is just something to help them get to an orgasm, because often, they might be too lazy to fantasise or maybe they just want some new fresh ideas (That is one reason I watch porn)
I would only be worried if your partner was addicted (Which it doesn't sound like he is) and was choosing to masturbate to porn than to enjoy sex with you.
I guess you have to find the confidence the believe that your partner is with you because he chooses to be. You cannot force anyone to be with you and people will not stay with someone if they are unhappy so he clearly wants you. You have to trust him on that. (Unless he has given you reason not to)
As for men looking at other women....ahhh they all do that! :D Its only when they take it further than looking that is is a problem. As I said, men are visual creatures, their eyes tend to be caught easily by pretty shapes, but (most) guys are decent and they have self control and they won't hurt you because they care about you. Its just the bad eggs you need to watch out for! lol