I am sure I've banged randoms with boyfriends but that doesn't really matter since its my style to never make a point of not talking about a girls guy situaiton. Now I am older I NEVER ask a girl when I meet her if she has kids.
I am talking about girls I know, and know the bf, and have banged. On 2 different occasions its led to the boyfriend threatening to kill himself over it. And both times that temper tantrum has resulted in the girl going back to him when I had her and she was ready to leave him for me.
Some of my biggest regrets sexually is only fucking certain chicks 2-3 times and not having a solid month of dating where I get to rail them 40-50 times and get sick of them. Its even worse now that I am 27 and so are the girls and if I somehow hit them up for a booty call via facebook I won't be banging anything as hot as back in the day.
On 2 of the hottest it was because of cock sucker pricks threatening to jump off a bridge to keep their girlfriend when they knew I had banged her (and telling their parents and having them get involved and shit.)
Men have no pride when they have a girlfriend they know is out of their leage and their loser asses knows they can't get anything equally hot. FACT.