Thanks for your advice everyone!
Well Mishka's problem seems better today.
I fed him some yogurt last night - he was VERY happy about that.
He does have all his shots and he does not have fleas but I'm still going to take him to the vet this week just in case.
(Oh, and he is 10 months old)
So I have another question;
Does anyone else have a cat that ALWAYS seems to be hungry?
Every time I step foot in the kitchen day or night, Mishka follows me in, runs over to his food bowl and starts to meow at the top of his lungs as if he was starving to death.
I have never had a cat that was THAT dramatic.
He is however much more vocal (and loud!) than any of the other kitties I've had...