Some people have issues with porn, can be addiction. Porn on an occasion is okay, I guess. Sometimes my husband will invite me to watch something with him....but I've never been into it much. It's grosses me out more then arouses me. I just let him do his thing, but like I said it's only been very few times our 6 years together. He'll ask before he orders a movie...since there 12 dollars a piece.
Definitely bring this issue to him, tell him how it makes you feel. If he's not willing to stop then cut off the Internet or something. If he reacts with rage then you'll know there's a problem.