Obsessive Guy rrggghhhh?

Alrighty, well there is this guy at my school. At first i thought he just had a little crush on me, so i didn't worry about it, but NOW it has gotten obsessive!! I really dont like him like that. He's a really sweet guy, but seriously, the constant IMs and corny sayings are giving me the creeps. I want to tell him to really lay off, but no joke, i am afraid he would kill himself. I'm not even kidding. Please help :]