My 7 year old Sheltie has not been eating for about 3 weeks. I took him to the vet a week ago and the vet gave him a cortizone shot to stimulate his appetite and some amoxicillin trihydrate/clavulanate potassium and some Nutri-Cal (high calorie palatable dietary supplement). It has been five days since the visit to the vet and now he is stilll not eating, not really drinking (I am forcing water through a syringe into his mouth) he is lethargic and he seems to be unstable on his feet. What could this be? I am going to take him back to my vet tomorrow, but was hoping for some sort of a diagnosis in the mean time. Thank you.