Have you been sick lately or had any reason why it would be feces? To find out for sure, wash your hands well, place a finger inside of your vagina, and pull it out to examine the color of your discharge. Sometimes it's hard to see, so wiping your finger off on a piece of toilet paper will show you the color of your discharge. If I were you, I would wear a panty liner or pad so you do not stain more underwear.