Okay, dude. We're coming down the stretch here. It's been a brutal fight, but you've made it this far. You, and everyone else here, have shown a tremndous amount of heart. RECOGNIZE THAT. Many people would've thrown in the towel by now. In fact, I'd lay all my earthly possessions and bet that some of the first to fold would be some of those smart-ass, no character having shallow jerks who parade as human beings. The ones with their sinister stares, evil grins, and "clever" insults.
You've taken some shots, but you're still here: STILL FIGHTING. And as long as you're fighting you got hope. I'm here to help with some between rounds advice (ala Mickey) to push you through so that you'll make it to that last, decisive round...
The disorder is trimethylaminuria. Known primarily as "fish-odor" syndrome, it has been know to come in other smells as well. Mine, for the most part, is the exact same one as you mentioned. I did however notice a handful of times the fish-related odor, also.
Primarily, though, it is the fecal one you mentioned.
My strategy: Many showers, ESPECIALLY after a bowel movement. There can be no other way. In fact, I have to take three (specifically, soaping that one area): the first two 5 minutes apart in the "same shower"; the third time about 10-15 minutes later (the "second shower") Excessive, yes. But nothing less has worked. Believe me, I learned by trial-and-error.
The best soap to use is a liquid, not bar, soap, specifically Aloe Vera type. All that bathing will be agitating to your skin; the aloe vera will do tons to keep that in check.
This may seem time consuming, but in reality it will take 20 minutes tops (not including bowel movement.) A small price to pay. It may seem excessive but get used to it. Pretty soon it will become part of your ordinary routine, like brushing your teeth.
ALWAYS take a shower in the morning before you go out, bowel movement or no.
Additional showers or quick rinse-ups in a bathroom may required as needed.
I have to go for now.
I will be back at the end the round...