I think the movie came out sometime before 2008, I’m not really sure.  I remember that the main guy is walking down a road at night after he leaves a party.  He was with his girlfriend and then he gets mad and leaves.  He sees a car, and it turns out he was murdered on his way home.  When he goes to his mother’s office and she can’t see or hear him.  He gets mad at her because he doesn’t know he’s dead.  Then he pushes all the stuff off her desk, but then he turns around and it’s all back on the desk like nothing ever happened.  He’s dead and only one girl can hear him, I think her name is Jess or something.  I’m pretty sure his body is in a lake and he needs “Jess” to find it.  She first hears him in a hallway in their school.  I really want to figure out what this movie is!  Thanks for any help!