Grr, please help! What's this guy problem?!?

Okay this dude is starting to freak me out! First we have never really talked except for a few days ago when he bumped into me and I said sorry, other than a few hi's, that's it. Then there is the constant staring! Oh my god! He stares so much, he will just turn around in the middle of a test and look right at me with no expression on his face. There was one day a few weeks ago when he barely did any work on his test just to turn back and look back. Then what is weird is that when he is around me he is clumsy, then in homeroom he will be okay talking to any girl or boy and just be fine doing what he's doing. So, what do you think is up??? Also in Math today my friend and I weresinging song paradoys and cracking jokes, when I looked at the clock I saw that he was looking right at me, while his friend was trying to talk to him. Also we are in High school.