It means he doesn't like you more than a friend guys aren't complicated like girls when they say or in this case shake there heads they mean it no complex mean when dealing with guys
Told my guyfriend i liked him and then he's like i dont no what 2 say...ok...at least u were truthful about it and then we hug and then i ask so do u like me more than a friend,he looks down,looks sad shakes his head no what does it all mean?
Basically he doesn't want to ruin your friend ship. He is being truthful because he doesnt' want to hurt you or take the chance on dating you because it could mess up the future. Keep god in your prayers, he will always be here.