Another vote for an immediate visit to the vet from me also. No cat will exhibit this type of symtom without being very ill. The only time this happened to one of my cats was when the Artful Dodger was in the late stages of vet-diagnosed renal failure. If you can't get in to see your regular vet, you should take your cat to an emergency vet, his condition is that serious (as far as we can judge online).