Why Does Stool Smell Like Burnt Rubber?

In the past week, my stool has been smelling like burnt rubber on and off. It started a few days after I noticed my lower abdomen was quite tender and sore upon moving. I ve also been having pain in my lower right apendix area and am unsure if its gas buildup or not. Do you have any idea what can cause this? Also, some side informaton, I have had my gallbladder removed and frequently have experienced abdominal pain since.