I have a 9 year old male Giant Schnauzer that's on the hyperactive side.
He is very obedient but 'anxious' compared to what he use to be. He even wimpers sometimes as if he doesn't know what to do with himself. He is more submissive than before too. He also shakes his head alot (ears are fine though) and is always hungry and thirsty. He is on the thin side and adding a whole extra cup to his daily food has barely changed his weight.
Also, he smells bad -even just a few days after a bath. His coat is dull and oily and flaky. His teeth etc are in great shape.
Could this be a thyroid disorder? The symptoms I've read for hypothyroidism are the opposite (weight gain, laziness, etc)
Do dogs get hypertyroidism?
I am taking him to get checked in a few days, I am just wondering if anyone here has heard of anything familiar.

Dogs can get Hyperthyroidism (far more common in old cats though) and yours has very suspicious symptoms! Get him checked out by your vet - if it goes un-diagnosed it can get serious. Hope he gets better :-)