Your pet is definitely not feeling well. You should take it to a vet as soon as possible. He might not have any digestive problem in the past that is healthy sign but loss of appetite is a definite sign of malfunctioning of digestive tract. One more possibility can be change in food. Did you change its food pattern or added something into it? If you did that then go back to its old routine. If not then try to slightly change its food to create its interest in that. Do not force it to eat anything. Try to make it comfortable by giving it more time. He may be under some sort of stress or afraid of something.
