Is porn cheating?

I just logged on to my SO computer to get my daughters medical documents. Come to find out he's been looking at porn. He does it when he's at home and I'm asleep and takes is computer to work, goes to McDonald and uses their wifi. Our daughter is six weeks old and she has been in the hospital for 3 weeks of her life. We haven't had sex since I've had her. Should I be upset he's doing this behind my back or is it ok because he hasn't had any since the morning she was born. I don't know if I should confront him now I have proof he's doing it or just let it go. Suggestions?