Okay people I'm facing a problem.

My back hurts.

Well that's not really the problem,it's just the result.My back hurts because someone constantly hits me there.EVERY. SINGLE. TIME.

He just casually tells me"How you doing,Petridi?"and hits me in the back.

Not like hit,hit.

More like greeting-hit.

Like today I was talking to a girl from the other class and he just walked towards me did this and went to the bathroom.

What. The. Actual. Hell?

Comment your thoughts please because I'm really confused about this situation.HE ONLY DOES IT TO ME!

And I thought that since he became more 'calm' this year,he would stop(last year he would sing him favourite's team anthem because he knows I'm a different team while having his arms on my neck and jumping)