I have had on and off fecal Body Odor for a year to two years, and have been odor free for two years. I'll spare you the horror stories of me sitting in class and everyone being disgusted, or the paranoia and scars sprouting from it. But I'm in a place in life where I have healed a lot and feel comfortable sharing information about my experience, and maybe it could help you out.
Symptoms: I wouldn't be able to detect the smell although it was obvious others were really bothered. They described it as poop scented and sewer scented and people across the room would be disgusted. I would be able to smell it for a split second in the morning when I just woke up, or if I was in an unfamiliar environment, or if there was another smell or perfume around, which was very weird. The smell would come and go. Most of the time I'd hear comments, but sometimes there were none at all. Went to about 7 doctor appointments, and all had no results and they denied anything I said. Being around people made me very paranoid and anxious, etc.
What worked in my two year experience and realizations: I was in high school with tons of schoolwork and hectic schedules. That lead to little sleep, high stress, and a bad diet which effected my body greatly. After constant research, remedy failures, and diets, I figured out that the problem was my anus and dairy consumption. My anus wasn't as tight anymore due to high stress, low fiber hard bowel movements, and also from sleeping on my back which put extra pressure on the opening of my anus. That was where the smell was escaping from. It had gotten into a red abnormal color and was itchy at times, which meant that I was leaking traces of feces. I started doing kegels and it returned to a normal tightness and color and it felt normal again.
That in itself solved smell problems but there was still the possibility of the smell still coming out. Long story short through many trials and diets, I realized that dairy consumption was the culprit of smelly poop. My body didn't digest dairy well. After eliminating it from my diet, I stopped having cystic Acne problems, slight congestion, and the sewery smell from my poop was gone and barely smelled anymore.
That's pretty much what I did and my life is stress free and normal again. I know it probably won't be relevant or useful to a lot of people but if I could help just one person that would be enough. If you guys have any questions please ask!