Hi doctor,I am a 31 yr old female had gallbladder removed three weeks ago ,it was full of stones,these last two weeks have been taking panadine forte and endone,as i have chronic back pain,doctor said could be post surgery complications but only time will tell,have been taking less tablets as the pain seems to be easing,but have had black thing mixed in with my stools and am not sure what it could be,i have watery and soft stools and have suffered with chronic diarrhea for six months,could you please give me an idea of what the black material could be,appreciate your time,Gabriela