I may have a theory, as I am experiencing the same issue.
First, your stomach is probably not producing enough acid to deodorize/sterilize the food you eat. As food is digested, the nutrients and waste enter the blood stream. The fecal smell is the waste from the digested food oozing out of the pores in your skin. Recently, I smelled a strong whiff of my own odor, then it went away...although other people could still smell it. In this case, the valve flap between the stomach and small intestines probably stayed open, allowing me to smell the smell. If there isn't enough acid in the stomach, your body doesn't communicate that the stomach flap should close...and it stays open. You talk, your breath smells of fecal matter/burnt rubber/etc.
I am testing the theory and a solution (have been for almost a year). The solution is HCL capsules, though I am still working on the right amount. I am taking 650mg capsules and also testing 600mg tablets (the tablets don't seem to work). Researching online, some people say take enough capsules to feel a "burning sensation" in your stomach. Basic instructions on the bottles state to take 1-2 capsules per meal. For me, none of those worked. However, starting when I wake up, I have been taking one capsule per half hour for 2 hours in the morning and around noon--while NOT eating anything/on an empty stomach--with some success. In instead of taking 4 capsules at once, which would upset my stomach, I gradually built up my stomach acid. It's tough trying to get through the day not eating, but not being laughed at/made fun of is A LOT better! The true test will be eating/drinking something and seeing if people can smell "the smell" 20-30 minutes after I have eaten. If they cannot, the test will have succeeded.
The last five jobs I had, people were making fun of/avoiding me because of the smell. This sixth job I currently have was in jeopardy until I did this.
Get HCL capsules at a health food store or online! NOW supplements are the ones I have. GOOD LUCK!