Does this Mean Anything at All?

My ex and I broke up and decided to stay best friends since we've been that for 4 years now and our relationship didn't kill our friendship.

Everyday when I see him, he always acts perfectly normal as he always does, but sometimes he suddenly acts real shy near me and smiles this shy, sweet kind & affectionate looking smile at me that he used to smile when we were dating. I'm confused. Should this mean anything to me at all?

Well when I was a teenage boy, I would be thinking about sex. I think what you are seeing is him having naughty thoughts about you and is trying to hide it.