Narnia,could’ve been me writing that. For ten or fifteen years my husband was the same.
Dentist said teeth were fine. I bought very expensive mouth wash,he always brushed teeth twice daily, but zero result.
Then he was struck with pneumonia, put in an induced coma, and on life support. Loads of antibiotics etc, and he pulled through.
His breath is perfect now, and still is 7 years on!! What on earth could last fifteen years and not “self heal?”
Something is very off further down. A good course of a decent antibiotic will hopefully solve it! Tell Dr whole story, hopefully he’ll give it a go for you.
Best of luck, please report back if you solve this problem! ???????????