You create more problems to your gallbladder and liver if you don't sleep well. I don't know where this idea came from, but rest assured stones don't move into the bile duct as a result of gravity. Sleep on your left side and take care of the stones by doing the liver cleanses. And you may suddenly find one day that your neck problems are gone (they usually disappear once the calcified stones are gone from the gallbladder, most often after 6-10 cleanses). Accidents easily affect the gallbladder meridien and liver zone near the neck, which in turn leads to gallstone formation. This again mimics the effects of the accident, but in reality are no longer due to the accident.
Enjoy your sleep on the left side. Your body type requires that.