HELP! Neutered Cat Spraying
So, I am at my wits end and need help! I rescued a semi-feral about a year and a half ago. I fed him for several months in my yard, then brought him in last winter. I kept him confined to a room for awhile until he adapted, and I had him neutered and tested.. He is FIV positive, with no signs of illness.
He's a super chill cat and enjoys the indoor life. I'm a rescuer, so I have multiple cats. He gets along well with most of my other cats with no aggression, and they are even playful with each other. One of my males does not like him, and there's some growling when they confront each other, but that's as far as it goes.
The vet estimates him to be about 4-5 years old. Prior to having him neutered, and for at least the first year he was with me he never sprayed. Then about 6 months ago.. the spraying started. I took him to the vet and he tested positive for urinary crystals and was put on a special diet and retested, and the issue was resolved. But the spraying has not stopped.
He sprays my walls, my blinds, my windows, my doors, etc. Ugh! He sprays multiple times per day.. I am constantly scrubbing something. His spray has no scent since he's neutered, but it's nasty and needs to stop. I've tried the plugin diffusers, Nature's Miracle, etc etc. Nothing works to make him stop.
I have run out of patience. The vet prescribed him Prozac because he said there must be some underlying stress issues causing the spraying, since there's no medical reason. I am not a fan of drugging cats, but at this point.. I need to do something. But, he won't even take the meds. He won't eat pill pockets.. if I crush it in his food he can smell it and walks away. I've even tried tuna and chicken, and he still won't take the meds. I really don't know what else to do.
Any suggestions would be greatly appreciated!