I had dark stool, nausea & light-headedness a couple days ago. since then stool is really light in color, very loose & have to go frequently. problem?

May need a Dr. visit: Dark brown color is normal. But BLACK stool may indicate bleeding from the upper gastrointestinal tract such as a stomach ulcer in which case you should see your physician quickly or go to ER. (Iron supplements and Pepto-Bismol will also turn the school blackish color.) In the absence of black stool the most common cause of nausea and diarrhea is a viral gastroenteritis. See a Dr if not better