Low weight after male cat's urinary blockage?

by Vanessa
(Thailand)

My male cat had a urinary blockage last October. My Vet tested him for everything and checks him 2 to 3 times per month (he still cannot urinate like a normal cat and can no longer spray).

He still has some episodes of going in and out of the litter box so it's like ongoing maintenance for him, especially as he has a small bladder and urethra.

My concern, however, is that he will not eat any of the diet foods, so I feed wet food. He eats well but does not put on any weight. He looks skinny. Before, his weight was around 3.75 kilos. Now it's 3.2 kilos.

Could this be due to stress, although most of the time he seems fine? Has anyone else had this problem?