It could be either..the sites or the porn.
There should be transparency in a relationship. You didn't do anything wrong..and it absolutely ok for you to ask him.
BUT...the best thing to do would be to go into stealth mode...spyware on his phone and a keylogger on his computer. Then you will find out what's going on...if you ask him it will tip him off and he will get sneakier.BS(me)42
M: June 2001
..that feeling you get in your stomach, when you heart's broken. It's like all the butterflies just died.