I'm not sure what to do about obsessive thoughts about him but I DO know you are not pathetic just because he does not like you.

Lets take Girl #1 - she's flocked over by pretty much everyone, gorgeous as anyone. But Guy A doesn't like her as much as Girl #2, who is less popular. Why? Because people are DIFFERENT. Maybe this guy isn't right for you (he might be GREAT but he isn't pulled by you right now). Maybe there's a guy who's pulled to you like a super magnet. Regardless, YOU are NOT pathetic because this ONE guy isn't interested