I agree that I think you need to see a Specialist. This may be a neuro and may be a back/spine/disc issue.
Something like this happened to my Mom's dog, they rushed him to the ER and did xrays and put him on Pred for a week. They followed up at the Specialist whom reviewed everything and ok'd him to go back to normal. But I have read too many stories of dogs become paralyzed, etc...
