Make guys who watch porn cheat

Watching porn - infidelity?

Hello, just first of all, my boyfriend is 22, we've been together for almost 2 years and also live together.
Our relationship is actually going quite well, often arguments, but at the moment it is actually limited.
He is currently on a trainee team trip on the Baltic Sea.
Since I sleep on the sofa during this time, he has offered me that I can watch films on his PC.
So when I was looking for films in the evening, I noticed the film "Perverse Investigation". Because of the name I'll take a look and find a really tough MangaPorno. I was totally beside myself and deleted the thing immediately.
Porn has always been an issue with us, because I basically have something against it, because I think that he has me and then doesn't need something like that.
We have talked about it many times, at first I always forbade him to do it, and he also said that he didn't need something like that and that he found it really disgusting. But recently I read in the Cosmopolitan that men find it crazy when they are forbidden to do so.
So a month ago I said to him that I would no longer forbid him to do so. I thought nothing of it, because he said that he would never watch something like that and thinks it is disgusting.
And now I find something like that in him!
Now I don't know how to behave, I feel totally pestered and betrayed. Also, I feel cheated in some way, I'm definitely hurt like hell, because I don't seem to be enough anymore (I'm VERY sure that he satisfies himself because he has done it before).
I feel very bad and have lost all respect for him.