Please tell me what I did wrong...?

Just ask if he wants to go someplace special to both of you (theres gotta be someplace since you've known eachother so long) it should be a place you go a lot and just tell him when you get there that your sorry if you made him feel awkward but you couldn't hide your feelings and want to know how he feels. Tell him if he says he doesn't feel that way you don't want to ruin your friendship and still want to be friends. Just pour your heart out and tell him.