Is he a lunatic or does he just have a crush on me?

He is 17 years old and I am 13 and on facebook he always IMs me and asks me what i would do if he kissed me and whether i dream about him. he goes to my school and whenever he sees me he smiles and shakes his head but his eyes are narrow. im scared he's almost like a stalker! or is he just in love with me?