Thank you for your sober advice.

No, no slip-ups since, as far as I know. He's done some measures for me to know what he's up to online and when we're apart (regularly updates, open-account policies, etc.) 

Yep, I absolutely wouldn't have minded it if it was just regular ol' porn use. It's the emotional aspect that bothers me, considering that these were girls he used to interact with (or is regularly interacting with in our circle) before and during our relationship. Some of them, he desperately wanted to bang or get into a relationship with.

I think he knows that the actions would hurt me, since he hid it actively and told his friends that he hopes I never see it. I guess he just didn't think it would be to this level of hurt, or that he wouldn't ever be found out.

Thanks again.