Chinchilla head tilt and walking in circles

I have a 4 month old chinchilla. He was born premature with a twin by almost a month and is about half the size he should be. He survived and everything was fine. He has the most active personality and was always bouncing around the cage. Yesterday night I went to check on him and he wasn’t hopping around and he was laying on him side. He got up and his head was very tilted to the side. And he was walking and circles around the head tilt. I picked him up and his head just kind of floped with little control over it. I can’t tell if he is in pain. He is eating but I haven’t seen him drink. I gave him antibiotics last night for an ear infection but he looks the same this morning. Should I have him put down? Any ideas? I stayed home from work today to see if I could get him into a vet but usually when I take my chins to the vet they are not very helpful and don’t give me clear courses of action or even really tell me what’s wrong. They use words like “it may be ...” any help would be great!