Ooof. This is a tough one. You betrayed him only to discover his betrayal towards you. What to do?
I went through something similar. Many years ago, snooping through my college boyfriend's things, I discovered that he was involved with someone else on campus. I didn't know how to approach him about it without confessing to my crime. But when he referred to me by the other girls' name not once, not twice, but three times, and the third time when we were naked, I never had to confess. That was the beginning of the end for us and eventually, we went our separate ways.
Your boyfriend has broken a very delicate bond of trust between you, especially considering your sexual proclivities. If I were you, I'd break up with him but not confess to the snooping. You don't owe him anything.
I just hope there are no photos.
Good luck.