How do you feel about porn? Not everyone is okay with it in their relationship for various reasons and that's ok too. Have you both discussed this previously? I would be upset about the lying too. It breeds distrust. Which isn't good for any relationship. I suspect he lied probably because he didn't want you to be upset. It's not a good excuse for lying tho.

I think it's really important to discuss topics like porn in a relationship and know where each other stands. Just like any other matter in relationships. If neither of you are clear where each other stands on issues things can get messy. Just like we all have different ideas of what cheating is and isn't, that can be a problem if we don't clearly define our boundaries to the other person and come to agreements.