I will only add this and please take in the best way. If you are not satisfied with your vets answer and feel it might be more, please see a neuro. We went through something similar in 2007 with our Kissie. Our vet couldn't find anything wrong, which I wasn't convinced. After many more days of Kissie not acting normal we decided to go to a neuro and found out she had GME which is an auto immune disease.
Your saying "just a bit humped over like he's afraid to move" is the way Kissie was. She was humped over, not wanting to move her neck and her tail under. That was our only clue.
I really do not want to worry you but GME is not something many vets have much knowledge of. I am lucky my vet doesn't have an ego and wanted the best for Kissie and understood our concerns.
Again, please take this in the right way. I am sure there isn't anything major wrong but please keep us posted.
