What is it if you have black stools but not completely only partially, i have no symptoms like severe abdominal pain or nausea, i have problems with constipation/diarrhea, i did not use the medicine or black food sometimes i even have mucus inmystool?

Test for blood: You should have your stool tested for blood. Black stools warrant excluding bleeding in the stomach or intestine. You may take a fiber laxative like Metamucil and drink enough water daily so that your urine is colorless. For the long term increase your intake of fiber foods. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948