I agree with Hammy. 6 times a day, even for a single man, is a LOT. The fact he's in a relationship and that it's coming at your expense amplifies it greatly.

To offer some further validations, I'm a twenty year old single male, with all the stereotypical expectations you could expect in that regard. I literally cannot imagine six times in one day...I consider 3 a major outlier. Six is near unfathomable. Granted, I am speaking for myself here, but based on my own knowledge and experience, six is certainly egregious.

There is nothing wrong with the porn viewing per se, provided you are comfortable with it and it's out in the open in the relationship, but the point that it becomes at your expense as a couple is where the line is drawn. Have you spoken to him about why he is gravitating to pornography so much?