Cuddling??

if he is 13+ he's old enough to want more than just giving you a friendly back rub. If you like him and he does it again, just dont allow him to go around front or down into your pants. Ask him casually "what are you doing?" with a laugh or giggle so you don't freak him out...see what he says. Maybe he really is just a good friend and is touchy..i know lots of people that are super touchy but don't mean anything by it.