After they get married Anakin wants to "prove" Padme and him aren't attached. Plus they both want to sleep with his master so the couple ask Obi-Wan to join them in bed. Despite being reluctant Obi-Wan agrees. Much to the couples' surprise he's a VERY skilled lover. So much so that Anakin gets over his jealousy and wants to have sex with him next. It's not that Obi-Wan has tons of lovers it's that he's pays attention and knows how to please. Much to everyone's surprise this leads to a very submissive Anakin.