what have i gotten myself into and how do i get out of this situation?

me and a friend of mine are sharing this dude, but the catch is he has a girlfriend
and all we wanted was pleasure out of the situation with no attachment... if someone falls in love someone else is going to get hurt in the end.... its not our fault that he's girlfriend is not doing what she's supposed to be doing to keep her man shit.... her loss is my gain so we are just having some fun......... so don't judge and i am not ready to let him go until i am good and ready ( ahahahaha i am a mess)