The good thing of him knowing is that that will, like, "plant a seed" in his mind, like he'll start thinking about it more and more!
I haven't met a guy that hasn't cheated on his gf/wife, and if he hasn't yet, he will in the future.
You know what's funny merla, I was thinking the same thing as you a couple of days ago! the only difference is that I just want to do him and that's it. Unfortunately he's married. He's young so, I'll just wait till the divorce. hah. jk.