first of all, your girlfriend's body is hers, not yours. you can't dictate what she can and can't let you do to it. if she doesn't like you touching her butt, dude, don't touch her butt. you just have to respect that. don't force yourself upon her. secondly, she shouldn't have to make exceptions for you just to make you feel special, if it means doing something that ultimately she doesn't feel comfortable with. i'm sorry but seriously, just leave her butt alone.