Well. You are 17, so by law he can't hurt you. But that doesnt mean he won't. Also most of the time guys are all talk but if you feel he is an action kinda guy then I'd suggest atleast taking some weapon to work w/ you in the car. A bat or whatever. Besides that I'd say hit that shit. I've had girls cheat on b/f's w/ me before, and the boyfriends really get pissed but none of them have ever actually fought me, although the little one tried to get his friend to... pff.