Hi,
Well, your poor boy certainly has a lot going on!
Has he been checked for bladder/kidney/urinary problems? Was it the vet who diagnosed the ear infection and is he now on antibiotics for it? The sneezing could indicate an upper respiratory infection or allergies.
You're very correct to suspect a thyroid problem or diabetes at this point, based upon his symptoms, but there are various other conditions which these symptoms could indicate, also.
The best thing you can do for your boy right now is bring him to the vet to have blood tests run and get a definite diagnosis, then the appropriate treatment will be prescribed and hopefully he'll start feeling and looking better.
Please keep me posted and let me know what the vet tells you. Thanks!
Cher
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