Bear is still sick

My black, long-haired 2 1/2 year old male kitty has a UTI and cystitis.
I've had to the vets 4 times since early Sept. The first time he had
been missing for aday and a half and came home sick with cornmeal
looking stuff on his back. I thought he'd been poisoned but vet said
no. Bear had a fever and vet gave me some charcoal stuff to give him
'just in case'. The next time he couldn't deficate after being missing
again. They had a hard time getting all the 'stuff' out of him. Then he
didn't get better and the vet being distracted b personal problems
thought he was having the same problem and didn't catch his uti. This
time she did so I'm giving him antibiotics twice a day. He hasn't been
eating anyhing except a little tuna and juice. I force fluids into his
mouth 3 times a day. None of my cats will touch the special food he is
supposed to eat. And he has lost 3 lbs!