My kitten, Jack, estimated to be about 18 weeks now, was neutered about 9 days ago and is still barely eating. He's around 5lbs and has only been eating about four tablespoons a day. He's also been drinking a lot of water, which I've never seen a cat do before. He is currently on pretty good dry food, as far as dry goes anyway, so that may be why he's drinking so much, but I'm worried that something's wrong with him. What should I do?