Hi thanks for asking question. Yes you are right normal mucus can pass in stool. If excess fatty diet taken then yes undigested fat can be excreted in stool. Second malabsorption syndrome like celiac sprue can lead mucus in stool.In this condition patient have sensitivity to gluten diet...like wheat , rye etc... Get your stool examined .As I also want to rule out parasitic infection like amebiasis or giardiasis etc.... If chronic constipation or obstruction then also by inflammation mucus can excreted... If you have associated abdominal pain irritable bowel syndrome might cause. Meanwhile take less fat diet with more fruits. If still cause not found then I will suggest you for consult doc for colonoscopy to rule out IBD or colitis... Take care. Dr.Parth Goswami