I'm an an awkward situation.

So, in the begining of mine and my boyfriend relationship I caught him watching porn... Not saw him watching it but I saw it on his searches on his phone. I brought it up and told him I think its cheating. He made an uproar and told me to get over it because it's only natural and it's a "habit". If we weren't serious I would not of cared.. Later on, I saw it again in his phone and brought it up. I told him that it is not okay, and that it really hurts me because I think it is cheating. He told me he wouldn't do it again, and I believed him.. A few months later I caught him. Again. And I was pissed. I told him if I ever caught him Again it would be over because he is lying and cheating in my perspective. He promised he was sorry and her never do it again. And then a few months later, he left his computer at my house and... I'm skeptical, I searched through his history. And I found more. I wasn't as much as upset as I was sad, I brought it up kindly and told him what I did, why, and how I felt. We had an hour long talk about it and how he is sorry, and he never ment to hurt me.. He promised me he would never do it again, he told me he wouldn't blame me for leaving him. But he said the that if I stay he would never do it again, and he would even stop touching himself when he's alone, to help prevent against it. I told him I loved him too much to leave him and accepted his terms. I don't know how I should feel anymore, I feel stupid for thinking porn is cheating, and stupid for going through his computer.. I have a very hard time trusting him now. Is it wrong to feel this way about porn? I don't watch it. My boyfriend said I should rethink the topic, but it's not my thing.