Its about a high school kid who gets killed by a girl and starts roaming around as a ghost but in the end he finds out that he wasn't dead yet he was bearly alive in a wood or something. The girl who kicked his and left him in the woods is the only one who can hear him. I also remember some scenes like ;
The guy yells you are going to get chaught and the girl yells back never not knowing who said it and the guy figures out that she can hear him.
In the beginning the guy imagines shooting himself in the head with a shotgun.
A bird hits somewhere and gets in the same situation as the guy (looks dead but then recovers) and the guy figures out that he isn't dead yet.
When he thouches stuff as a ghost they move but when he looks back they are the same as before.

The Invisible (2007) (http://www.imdb.com/title/tt0435670/reference)