Can someone try helping me figure out what's wrong with my dog?

I have a yorkie and he's about 4/5 years old. He all of a sudden started panting and shaking and wouldn't listen to us. So we took him to a animal emergency clinic and they couldn't figure it out but they gave him a shot which he was able to calm down and sleep for the night. But the next day it just started up again. So we took him to our vet the next day, took blood test and everything is normal. They gave him a bunch of pain medication that was working some what for a little bit till today. He started laying down panting again, not really wanting to get up and when we walks he stumbles and almost fall. I don't know what to do! We already spend 700 dollars on my dog and he's not getting any better. Any advice?

It sounds like he is having seizures. There is nothing you can really do about this but be there for your dog when it happens. (I could be wrong but that's what it sounds like)

Your vet needs to go further. Panting, shaking is PAIN (so it is normal for the animal not to listen to you because it is badly hurting!) and are symptoms to a load of different diseases and illnesses. I would get back to your vet, ask for a FULL blood panel, x-rays and possibly even an ultra sound, MRI, whatever and if you need to see a specialist, then do it.PAIN medication is only masking the problem. Need to find out WHAT the problem is and treat it accordingly.It sounds neurological if he is having trouble with walking and falling.