How can I get my boyfriend to stop displaying such poor manners and being so disgustingly in public?

My boyfriend has horrible manners in public. He will cuss loudly when telling a story I don't even care to hear about how his "friend f**ked some girl" within earshot of little kids. He burps loudly in public...farts in public...he will even stick his hands down his pants to "adjust" himself complete with "ooohs" and "ahhhs" IN PUBLIC. He points at people and talks loudly about them to where they could easily hear if they were listening. He makes crude jokes that only he finds funny. I've tried to talk to him about it, but he'll just blow me off with a "who cares" type of comment. He didn't used to behave like this. We've been together 8 months and it seems like the more comfortable he gets with me, the worse it has gotten. He acts like this at home, too, and I don't feel like I reenforce it in any way, but it seems like he is almost putting on a show while were in public. Everything gross he does increases ten-fold when there are strangers around and it's starting to get way too embarring for me to handle. I feel like I'm scolding a child. It's such a turn off for me! I don't know what to say to make him listen without him thinking I sound like a complete b*tch. He treats me like a princess, but he's just so rude to the rest of the world, what can I say to him?