I have 2 male cats. They were at the vets 4 weeks ago for a detnal scale and polish and since the return I of the cats is ill.
He will not eat his dry food, so I have put him back onto meat.
I don't see him drinking very much (unlike the other cat)
He is moulting a lot.
He has started to go to toilet in various places around my house despite a clean cat litter tray being available to use.
??

So funny you say that... I've had a cat that did this similar behavior before... I had went away for a week and had paid someone to go over and spend time with my cat a few times a week while I was gone... but I guess it wasn't good enough... he was really mad about it all and for about a week after I got home he wouldn't come near me or eat his food and just acted like a big baby... not saying this is your problem but it could possibly be just that... other than that call the vet and get his opinion