Help >_o, Problems.. Options

[Kanoki]

A guy in my school who I took to be only some kid who I had science class with is making my head rush and making me all twitchy when he instant messages me online to just say "hi" and for me to give a choky saying of, "Oh hey..".
I hate the feeling.
The other thing is how he always says hi to me at school with all his guy friends. I'm a social outkast so to speak so I'm not exactly flattered, but I can't help it, I like him and I can't take it.
I try to push him away by 'accidently' tripping him in hockey, kicking his shins in soccer and constantly arguing with him in MUN (some debate thing in my school), but it doesn't seem to harm him. He's just always there, grinning in my face and asking to offer me some help. If my reluctancy to admit that I'm crazy for him continues, I'm going to be sick.
Some help please? (I know I'm new, but I really need some advice and I kow I sound a bit whiny..)