Is my Boyfriend Cheating ?

I think sometimes when you've been in a long term relationship you can fall into a routine. Maybe he has something on his mind that can't allow him to perform in the bedroom the way he normally would. That's why he resorts to porn to relieve himself. But that doesn't mean he is cheating. I get why you might get that impression. But if this is the only reason why you think he might be stepping out on you, then maybe your jumping to conclusions. Unless there are other signs that would make you wonder. I think you should talk about it. Ask him if somethings troubling him. Or why would he resort to porn when he has a willing girlfriend at home? Be open with each other. But don't jump to conclusions and let your mind get the better of you.

Hope i was able to help!

Was he always like that or is this a recent change in behavior? He might not be cheating because porn can use up the desire for sex. He's fulfilling his needs through that so doesn't need as much.
I would talk to him about it. Be honest and say you are worried he doesn't find you attractive. Maybe the two of you need to discuss ways to spice up your love life. Sometimes when people have been together a while it can get a bit routine.