Am i wrong for getting annoyed at my SO watching porn when he is not with me?

He has no reason to, i send him pictures all the time. it makes me feel like i am not good enough. But hes looking up stuff like Hot Blonde Teen Gets Rammed. like nasty, dirty stuff that i feel so uncomfortable knowing he looks up. It bothers me so much! but i asked him how he would feel if i watched it and he said its like cheating! but he does it at work, or wherever when he is not with me. Am i wrong for asking him not to watch it? Am i wrong for not feeling good enough? Our sex is DEFINITELY NOT boring what so ever. So why does he feel the need to watch it? i know "guys will be guys"...