Why don't boys like me mire than a friend?

well I haven't had a boyfriend for ages and I'm a 13 year old girl, umm my bestfriend that is a boy, when he inboxes me on Facebook he often puts x"s after he talks does that mean he likes me cause he also puts smiley faces so I put smiley face back. does that mean he likes me? should I ask him out? wat happenes if I ask him pit and he says no? please help me :) I desperatly need help :)