Sometimes i have a dark stain on my underwear after i have soft poop. but this only happens 2-3 hours after i go. i notice that this doesn't happen when i eat more fiber and less fatty food. would fiber/diet change clear this up?

High fat diet: A high fat diet can cause oily stool that tends to seep out after bowel movements, thus leaving a stain on your underwear. Try avoiding fatty foods (cheese, fried foods, high oil candy such as gummy bears, and oily meat dishes). Eat a diet filled with high fiber fruits and vegetables and drink 2-5 liters of water daily. Take a probiotic to further regulate your intestinal flora.

Could: Fat malabsorption could be causing anal leakage. It would be worth a try to reduce your intake of fat and increase intake of fiber. Consult this site for fiber foods. http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/high-fiber-foods/art-20050948 Wish you good health!