Your girlfriend and her friends want to dress you up as a girl for a week because your parents are away and they are coming to stay she says it will be fun theres no way back now what should I wear?

This is a little strange. Do they want to put you in a dress? Walk you a round in a bra and panties? Or just put make-up on you and play around. If they are going to dress you, that sounds like you might be in your underwear or naked in front of them. See if they will be in their underwear or naked in front of you! That might be fun. Bottom line, if you feel uncomfortable about it, don't do it.