I don't think you're being selfish.
I've been in the same boat. I've found porn on our computer many times over the years and wondered if I too, was maybe being silly or insecure.
There was a time where I would get very angry about it. We'd have major arguements. He would be upset I was "snooping" and I was upset of course that he was being aroused on a regular basis to all sorts of images and videos he was finding online.
After a while, I gave up. I even tried to be understanding about it. I felt like before I had made him out to be a pervert and put him on the defense. I know that lots of men do look at porn, so I tried to make myself okay with it. It never happened though. Everytime I found it, I still got upset. And even worse, since I appeared to be okay with it, he began doing it even MORE! Our sexual relationship only got worse and worse. He began coming to me less often for sex, and when we did make love, it was not affectionate or like it was. I could tell he was having a hard time, and that he had become so accustomed to masturbating to porn that it was hindering our sexual relationship and affecting our marriage overall, because I began feeling inadequate and resentful.
A month ago, after finding marriage builders, and reading a couple of Dr. Harley's books I broached him about the porn issue (and a few others) I told him how it made me feel, and that I would like for him to stop. I did it very nicely, I didn't get angry, I didn't make demands.
It actually seems to have worked. I do still "snoop" to see if he has been looking, and he hasn't, for a month now, which is extremely good. He was looking at it everyday prior.
Sorry for the long response. But I just wanted to share my experience and insight on this. Again, you're not being selfish. You have every right to be upset by this. I don't think pornography is always bad, but I do know it can cause big issues in a relationship depending on the man looking at it. Some guys look infrequently, it never becomes a problem. Others like my husband, have big problems with it and it becomes an addiciton.