Hi, I am a 62 yr. old female. For last 4 months, I ve had half inch cube like masses in my stool . The cubes are covered with a yellow/green mucus membrane and now the mucus is covered with a bright red blood membrane. The mass floats. The inside of the cubes is a chalky substance much like a white tylenol tablet cut in half. I have sharp and constant pain in my left colon area after they pass. What is possible cause? My thought is that medications which I take in tablet form are not breaking down. Thank you for your expertise.