Why would I have persistent nausea, and I'm not pregnant or sick with anything the doctor could find?

Nausea causes: many. There are many causes for nausea. If your doctor can not determine the cause, you may need to see a GI specialist first and other specialists if the problem is not gi. If you are on any meds, one of them may be the cause. Nausea may result from problems in the brain, ears, eyes, or blood (like low blood sugar or carbon monoxide). Many conditions can cause nausea. See your doctors!