How do I get this dude to STOP texting me every 5 minutes?

Okay, So I am basically dating this guy, but his friend has a crush on me. I don't really like his friend cuz he's a complete jackass (Just being truthful). He texts me ever 5 minutes and to be honest... He's OBSESSED with me. Also, when I don't respond RIGHT AFTER he texts me he FREAKS! Like what the heck? And he's still a lil pissed that I chose his friend over him. I want to kindly say lay off (cuz remember, its his best friend) so I don't necessarily want to say fck off. And I don't want to turn off my phone because that's my bf's only communication to me. So what's your advice?