I truly believe it's just a completely normal guy thing. Doesn't take away from his feelings about you. They have a lot more sexual urges and impulses than we typically do, and for many many guys, porn is a routine part of their solo sexual time.

Most men are visual, highly sexual creatures. I wouldn't worry about it or feel threatened by it unless you notice that he's spending an obsessively heavy amount of time surfing porn sites and no time at all interacting sexually with you. If he's still hot for you and your intimate relationship is good, just think of the porn as a harmless masturbatory hobby.