My yorkshire terrier screams, shakes for no reason

Question
My yorkshire terrier is 2 years old.  She has led a happy life.  It was not until 2 weeks ago that she starts to scream, shake for no reason.  She does that at random time, sometimes in the middle of the night or just after dinner.  She may start screaming or shaking after being held peacefully for 10 mins.  When brought to the vet and performed full scale check up including blood test, ultrasound, x-ray and everything, it was opined that she was physically perfectly fine.  We have no idea how to heal her.  When she screams, she looks really painful.  But after 30 mins or so, she behaves completely normal.  What's wrong with her?

Answer
I would guess, since everything else has been eliminated, that your Yorkie is in need to chiropractic care. http://www.avcadoctors.com/search_for_avca_certified_doctor.htm  Unfortunately, there doesn't seem to be anyone in your area who can do this.

She may have a vertebra out-of-alignment or some tight muscles that are bothering her. I would try to gently massage her a couple times a day, and if you can find an area that seems to bother her more, try putting heat on it twice a day.