Saw something I shouldn't have when snooping. Advice?

I know, I know, snooping is bad. I shouldn't have done it, but I did. And low and behold, I found something uncomfortable. I managed to get into my boyfriends email only to see that he was conversating with another male in a ual manner and asking about when and where they should meet. Naturally, this is pretty heartbreaking because it's never fun to find out these things, even if you shouldn't know in the first place. I had a feeling that he may have been bi-curious, though he never admitted it when I brought it up. I'm bi myself, so, it's honestly not the fact that he is speaking with a male...it's just that we are dating and he is going behind my back. I would never cheat on him with another male or a female regardless. This could run the risk of STD's, so naturally I am worried about my own health and safety. I love him to death, but I am very scared. I'm not sure how to go about bringing it up or even if I should, especially since I was snooping in the first place. I also want to think that maybe he's just talking junk...maybe because he's a little excited at the time and he's curious...I want to think that he will never actually go through with it...but who knows. Anyway, I'm almost certain there is someone who has dealt with a similar situation and I'm hoping maybe someone could offer me a piece of advice, it would be greatly appreciated. I'm beyond terrified and confused.