My rabbit won't move!

My rabbit won't move and will just stay in the same place for hours!! he won't eat on his own, only when I hand feed him. When I put him down he just flops over and will just lay there and not move. He's not using his back feet either. Just won't walk. Usually when I let him out of his cage he is running around chasing things but all he does is lie there looking dead :/ , I don't think he has diarrhea or anything. WHATS WRONG WITH HIM? PLEASE HELP!