welcome to health care magic forum,
from your symptoms it seems that apart from motion sickness
you have to look for other problems which can cause this type of symptoms.
if there is some problem in the ear it can cause vertigo
which gives feeling of nausea
and stomach upset
feeling,while turning your head or nodding your head as it is in your case.
if you are above 35,there is possibility of cervical spondilitis which again gives same type of feeling.
you are advised to consult your doctor and discuss above points.