Calling me by another name?

My boyfriend, who I've been with now for six months, keeps calling me by another woman's name. I am not talking about him accidentally calling me someone else's name during sex. He has done this since day one and I've expressed numerous times that I don't like, not to do it, and to ask why he does it. He's still doing it. He almost says it in the way that you would have a pet name for your partner, only why would my pet name be another woman's name? For example, if my name is Gina, then why does he jokingly call me Penelope? For example, if we were getting ready to go somewhere, he would say, "come on Penelope", or "good night Pumpkinhead". Also, he calls me something like Pumpkinhead, or Punkarella. Never does he have any sweet or loving pet name for me, and won't call me by my real name at all. Any help with this one?

Have you asked him about it? How does he react? Ask him to call you buy your name.