Assuming its not pregnancy, it’s sometimes a little tricky to track down dizziness problems since all sorts of things cause dizziness, and dizziness almost always causes nausea. Dizziness and nausea are commonly caused by an inner or middle ear problem, but lying down typically helps, and ear problems would not be affected by eating. Since eating seems to affect the symptoms, and lying down makes things worse, this suggests that the problem could be related to the digestive system. The problem in the digestive system that is most likely to cause these symptoms is a hiatal hernia. Your symptoms can also be caused by a partial blockage of the coronary artery, so its probably time to see a doctor.