WHAT DOES IT MEAN WHEN A GUY CONSTANTLY STARES @ YOu?

It all started last yr when I was just walking down the hall and said to his friend "who's that?!" and he ment me. Later that day he added me on fb and started commenting on my statuses and joining my groups etc and being all nice and stuff. I guess you could say that he maybe liked me but then this year he hasn't paid much attention to me until recently(January). He and his group of friends stare at me alot and he does that too and sometimes they kinda smile while staring. He'll talk to his friends and than his friends look at me and they look down.,, one of his friends looked at me and than looked away when I caught him. And his friend was talking to his friend and looking down and smiling than looking @ me. And the guy that liked me once tried talking to me and he was like do u want this and he had a gummy beat loll and I was like errr no?... Lol anyways I think kinda discouraged him from talking 2 me or sumthing and one of his friends sed he's intimidated by girls. Today in gym I was talking to my friends and he ped by looking straight than turned around and looked at me than turned around and looked at me again. Once i was just standing beside my locker and i turn to the side and i notice him looking at me while he's walking by but than he quickly looks away and i was also once talking to my friend, and he kept looking @ me and i caught him and he looked for just a bit than quickly looked away. wtf? I don't get it y does he do this, but sometimes he wont do anything at all. its making me self conscious.