i'd say be up front, if he isn't down for it let him walk, the more lies and hook ups behind his back will only make it worse and probably cause him to react negatively. In my case wife cheated on me for 6 mos, but we'd been swingers so it was less of a big deal, now i've been her faithful, fully on board cuck for over 15 yrs, but all guys are different. As they say in commercials, "Your results may differ..."