Boyfriend Watching Porn: Totally Natural or a No No?

So, I've always tried to be cool about porn, and I like to watch it with my S/O. But my current boyfriend and I have each other's Google account stuff, (no, not a trust issue. I'm basically his personal assistant and he is too busy to actually read his email), and I keep seeing porn in his history at times when I'm either asleep or just not at home or whatever. And it's bugging me... a lot. I ask myself if he was thinking of me while doing it, if he "got there", it just in general makes me question myself. I've never had this problem before, in fact I've usually always laughed when I saw it on an ex's history. Anyway, my question is; how do you guys view porn when in a relationship? Is it really just a natural thing and I'm being crazy?