What's wrong with my chihuahua??!

What's wrong with my chihuahua??

He is a 7 year old chi. He started crying one night and panting, racing around the house, would not sit down...Long story short, I too him to the vet. They did blood work, xrays, anal gland check up and expression..etc. They found nothing wrong, except for the fact my dog acts like he's on crack and in pain. He has taken prednisone for a week now but that makes it worse. Is it pain he is in? Perhaps his legs, knee patella luxation, spinal injury?? AHHH..I don't know what to do. It already has cost me $350 at the vet for all the tests. Help. Give me ideas to at least google and research. I hope it's not neurological.

1 month ago
Sorry I put this in the wrong place in the forum. Forgive me. I will move it...and yes, in response, my dog is pooping but he is very hesitant about doing it.

Just a quick question. Is your dog pooping? A friend of mine had a Yorkie who did that. It turned out that the dog had eaten a wad of hair from the garbage that my friend had cleaned from her hairbrush. The hair got caught in the dog's intestines. The vet had to do surgery to clear it up. I certainly hope THAT isn't the problem.