I mean little as in a child. Like it or not, you are a kid. And for a twenty year old MAN to stalk you (there's no question in my mind that he is stalking you) means that he is most likely a pedophile.

This guy sounds like he wants to hurt you. Stay far away and tell your parents ASAP!!

Just wanted to add:

A twenty year old man who preys on thirteen year olds probably does so because all the girls his age think he's a loser. By picking younger girls he hopes they won't notice what a freak he is.