What's wrong with him?

My horse has been laying down all day, and he wont get up. He just grunts when I try to pull him up. I even tried spraying him in the face with the water hose but he still just laid there. I don't know whats wrong with him. It can't be colic because he doesn't get grain, he gets a flake of hay everyday. It can't be founder because he's really skinny. He hasn't been limping or anything so I doubt he's lame. Plus he lives in a stall so it's not like he hurt himself running around the field. I don't know what to do. I don't have the money for a vet, and even if I did there isn't any in the area. So don't tell me to call one, if I could I wouldn't be asking you. Please please tell me whats wrong with my horse I'm really worried.