[dwerten]

I am just seeing this and honestly think you need to get your dog to a neurologist based on the dogs age there are a few things this could be and sounds neurological especially since nothing showed up on xrays as your dog may need an mri and spinal tap. Blood work can come back normal and a neurological condition can be there.

Is your vet consulting with a neurologist? Please ask

If it is neurological the sooner he gets treated the better the outcome