I was looking online the other day and I read a comment from someone who wrote to a Dr. Kevin in a Gastrointestional forum, I think it was called Med Help.
Anyway someone wrote about having a fecal odor problem but they also complained about burning and itchng in the rectal area. And the doc mentioned several things but one that stood out was "Anal Fissure".
I don't know if you have this problem but there were a couple of other ailments mentioned but when I read about it I didn't recall you saying anything regarding burning or itching but from what I read sometimes a little bleeding may be involved.
Maybe this is something worth looking into. They say people can get them by not having proper bowel movements as well. They mentioned different treatments but I thought about you and thought that this maybe similar to your situation, because some people have complained about bowels smells and some were diagnosed with anal fiisures but not necessarily infections. What I've learned is a bowel smell underneath dosen't necessarily mean infection, I've got a lot to learn, God bless.