For the last few days I've been getting waves of nauseousness. I am not pregnant, don't use drugs or alcohol, not taking any medications. Thoughts?

Virus? If it has only been a few days it is likely a virus or food poisoning? If it persists, go see your general doctor. There are many possibilities.
Gastritis, or possib. Lt gallbladder disease. Check with your doctor. Nerves can do this to you also. All possibilities should be looked into.