Why is this guy stalking me?

Hey so im 15 and this guy is stalking me! like seriously one day he followed me and he is always staring at me. He constantly comes up to me and i told him to not be so creepy. (btw everyone in school thinks hes a real creeper). Well he is constantly talking to me and everyone is telling me to be careful and i told him to go away.. he left me alone for 2 days even though he stared at me all the time.. but today he creepily talked to me again. (our conversations involve: him saying im not a stalker, him asking me why i think he was a stalker ect ect) how do i make him stop??? help