Have you tried benzalkonium chloride wipes for your pits? Supposedly kills funky bacteria.
I mentioned meat before, but also vitamins can create stink. If you take them on trail, don’t take more than 100% RDA. The B complex ones can really make you stink. You might need vites on something as long as the PCT though. Just don’t overdo it.
Are you considerably overweight? I don’t mean to be prejudiced at all, but I have noticed that people who are morbidly obese often have terrible BO. Don’t vote me off the island here; I have lots of compassion for people who struggle with weight, including myself.
Whatever you do don’t use deodorant/antiperspirant with scent. Perfumes and scents just make the smell worse. It’s like the scent takes the funk and broadcasts it. Guys who wear Polo or Axe – I have to keep them at quite a distance to be comfortable. I actually prefer the smell of sweat. Probably true with scents for women too; I don’t know anyone who uses scents!
Ditto with tobacco; hopefully you’re not a smoker? My tobacco allergy gets worse with every exposure and I now unapologetically move away quickly, before i break out in hives. I was recently on a flight sitting next to a guy who spent the entire flight dipping from a pouch or sticking a cig in his mouth and getting scolded by the flight attendants. He smelled so bad! We nicknamed him Hacky because he had a deep horrible hacking cough. He was wearing a joker mask too, which didn’t make me any fonder of him.
I use a drop or two (no more!) of pure bleach to wash my clothes in a ziplock bag. The rinse water gets dumped far from trail and water sources, usually over a big boulder.
I hope you find some solutions!