I think I am crushing on my ex best friend 

 Last time we talked as real friends was 2 and a half years ago 

 We go to the same school so I have always neglected him for the past 2 years because we ended our friendship tragically...
I went back to school a few days ago and he's in almost ALL of my classes 

 he kept staring at me, and once I caught him doing so but he didn't look away. 

 I don't know what to do. 
