I think its about a girl feeling confused because her guy suddenly changed on her. She does not know where she stands in the relationship anymore. Its some kind of a post break-up song, at the stage when the guy gets all cold for some reason and she does not bother to tell the girl why. Its a sad song. It makes you think of all those times he closed up like a clam and made you feel desperate to fix things up without knowing how or where to start.