If your bf is really cool with this, and he wouldn't consider it cheating, why don't you tell him about this? If it isn't cheating, you have nothing to hide. I'm a pretty sexually liberated person, but one thing I'd never tolerate is cheating. It isn't the fact that you fooled around, or fucked him. It's the fact you deceived him, the fact you did it behind his back. If this man puts all his heart into loving you, and you turn around and screw another guy, what does that tell you? If it were me and I found out, I would walk away. No questions. What you could do is ruin a great thing you have, over temporary pleasures.

Were all human, we have desires that we must resist, and sometimes we succumb. But there's no way to justify these actions.