What should I do, I'm not sure if my bf is being sexist, and I don't know how to confront him.

My boyfriend and I both have always had the same view when it comes to girls. We both think girls are typically bad drivers, ruin jokes by pointing out what's funny about them, and etc. I have no problem with it. I've always been open about hating the, if you will, stereotypical stupid girl and making stupid girl jokes. But recently he's been starting off jokes by saying, "you won't think this is funny because you're a girl" or "you won't get this because you have a vagina" and so on. What use to be our ground for making jokes about girls being stupid, I feel is now turning into a ground where he feels its okay to insult me because I'm a girl. When I've tried to confront him about this, he gets defensive and closed off; it's so frustrating! What should I do?