Kitt's not feeling good, what might be wrong

I have owned Kitt for 10 years,  and I know his personality like the back of my hand.  For the past 3 days, he has been extremely listless with an absence of appetite.  He has spent nearly every minute of the 3 days sleeping in a back room,  just the opposite of this very active cat.

He is walking fine,  his ears are not hot, and he still purrs when I pet him.  This odd behavior has me worried,  but I have no money in my budget for an expensive trip to the vet.

What could be wrong with him?

He probably has an upper respiratory infection, which is extremely common about 10 days or so from bringing a new kitty home.  The stress of a new home, new sounds, new routine, and new people seems to trigger these outbreaks.  Get him to the vet for a check up and some meds (but don't let them give him a Convenia shot or Metacam...read more on the board here for info) and he should be back to normal in a few days.  Good job of knowing when he's "off" and not feeling well.

The OP said he's has this cat for 10 years (not 10 days).

With that said, anything could be causing this behavior, and it's virtually impossible for us to know what's wrong with him. He really needs to see a vet.

Just so you know, a cat that goes over 48 hours of not eating is at risk for developing hepatic lipidosis (fatty liver disease), which can be fatal.

Check out this link: http://www.thecatsite.com/t/155462/cant-afford-a-vet-please-read