@Bi-Polar Bear,
Oh, now I remember I suggest you take the cat to a vet before doing anything else and you for some reason did not react well to that suggestion and make some comments that set me off as a cat lover that later you claimed you did not mean.
Fine still it is over the top for three people to offer attacks for offering sympathy months later.
If a cat change his or her behavior such as not using the cat box after doing so for years the first thing that I would suggest is taking the cat to the vet.