Sick chinchilla barely eating, drinking and inactive

My chinchilla suddenly became motionless two days ago. He ignored treats, food and my prodding. I took him to the vet, who diagnosed a heart murmur and eye infection. He was sent for an ultrasound. He struggled a lot and they could only get clear views of one side of his heart, but the vet said there seem to be no abnormalities. Since then, he has been barely eating, drinking and moving much. He is not chewing sticks, his usual favorite activity. He also hasn't closed his eyes and lay down to sleep for 2 days (He usually does every day) He accepts treats but refuses critical care.

Does anyone know possible reasons for his behavior? Could it be due to the antibiotics or eye infection? And I don't know if he is not eating due to bloat, the vet said he does not have bloat, but maybe he developed it after due to the stress? Can I feed Simethicone with the antibiotics? Thanks all. I am very worried and hope somebody can help.