I would say you need to talk to him about it. He's the only one that is going to be able to give you any information that is valid. Share your feelings about it with him. Divine does bring up a good point...do you still have memberships? If so, maybe you both need to do some thinking about your relationship and where you would like it to go. If not and you just looked up his computer history( or whatever the case is), you still need to have the same convo...what do each of you want out of the relationship and where is it going. If he is not willing to stop looking up women, regardless of his answer, its time to move on. But, please, do have a meaningful conversation about your relationship...no blaming, no accusations....just converse to understand one another.