What does it mean when this boy keeps on bothering you?

In most cases he is infatuated to you and has a big crush on you, explains his obvious move of following with your knowledge. But sometime it could be adverse- could be he is a sex addict, a thief, a robber, rapist, psychopath, compulsive stalker (harmless but addictive, yeah there is such a thing as compulsive stalker) etc. I would suggest that you try to get some background check on the guy and if feedback seems normal you may confront about why he is a stalking you.