help chin not eating or drinking

Just wondering if anyone has ideas what I can do to get my chin to eat. Its been 3 days of not eating or drinking. We were able to get a little critical care down him but not much. We took him to the vet and he took an X-ray and said it wasn't impaction. He did see a small pocket of gas. But he isn't pooping and the few he finally did today and they were SUPER small and deformed shapes. we have been giving him simethicone 3 times a day. We are very worried he is going to dehydrate if he hasn't already. He still has energy and will run around.

He has lost about 20 grams….Can I feed him pumpkin without it hurting him?