Hi,
Natural hormone changes during your period can cause nausea; if it's extreme enough to cause vomiting throughout the day, seek advice/treatment from a doctor. You could always take a pregnancy test for a more accurate answer, as to whether you're pregnant or not. Otherwise, you might want to consider treating your nausea by using remedies at home. Drinking Ginger tea (mix 1/2 teaspoon of ginger powder or fresh ginger slices to 2 cups very hot water, let cool for a few minutes before drinking), or Peppermint tea (boil 3 cups water, add 10-15 peppermint leaves, let steep for 5 minutes before drinking) can help settle your stomach. For more recipe ideas, google home remedies for nausea... When you do feel like eating, keep the portions small and bland, for example: a handful of apple slices, crackers, bananas, rice, toast, yogurt, applesauce, etc. ~ stay away from heavy, salty, or sugary foods... You could also use a dose of Pepto Bismol or Mylanta for quick relief of nausea. Applying a cool, damp washcloth to your forehead while resting with your feet up, can really help too. Basically you'll want to take it easy and keep your schedule light during this time. Take Care