I read your story and noticed some points why he possibly acted that way now.
First, you said you became clingy and because of that he changed his mind towards you and your 'relationship'. No one likes a clingy girlfriend because it is very annoying to the other person. In addition, he is not yet your boyfriend and he is just in the stage of showing interest in you without yet meeting you personally. Your clingy personality was the dominant description that he knew about you even from the start and it is bad and it created damage to what he possibly see in the 'relationship' that is sprouting.
If you really want him to be your boyfriend, you can change his outlook about you.
You said you are communicating through FB? Then, do this through FB too.
Post things about happy relationships, love quotes, life quotes, your life updates, your pictures with friends, etc without mentioning him. Make him like you and make him find love through your posts. Make him like you or love you by creating your own personality through your FB updates. When he ask you something, reply to him naturally. Avoid being clingy. Love will bloom eventually if there is magic or a chemistry that exist between the two of you.
~ love educator and relationship expert