Im gay. my friend doesnt no. i want to "F" him?

he pretends to "f" me up the *** wen we hav cloths on once in a while. we tak showers together. wen i say dont strip he does a little dance barly pulling down his boxers. then one day 2 months ago i accidently grabed his crotch and then it became a game to see who could grab the other guys crtch first. he says hes straight but i dont no he has a girlfriend. how can i convince him to f me.