Has anything changed? Have you moved, gotten a new pet, gotten married, had a baby, etc.? So many things can effect a cat's behavior. I know that adding another cat to our home sent Mimi running...she didn't "mess" the way yours is, but didn't want to even come indoors.
Give us some more information. I'm sure someone will have a good idea. Also, you should check with your veterinarian to discuss this issue. Something is wrong.
Logan