If it's mostly nausea, then I think it's probably due to stress or a virus.
I know I get nausea at night before I go back to school at the end of breaks or whenever I'm nervous, even if I don't really feel "stressed out". The nausea at night can be dealt without medicine by sitting up for a few minutes, cooling down and relaxing, and then laying down curled up in a ball on my stomach with my head elevated, and slowly rotating into a sideways position and falling asleep.
Nausea after eating also happens to me sometimes. I don't know if it's because I eat too much, the food is too rich, I ate too fast or what. I know I get very hot and sick to my stomach. Cooling down is often the best solution in these cases. Right now I just go walk outside in the snow. Sitting down also helps, with a slight lean forward.
You can also try tums or pepto bismol to lessen stomach aches and pains, though honestly neither have ever worked for me. I've thrown UP pepto before!
