I too have had this problem for most of my life. After reading sanclembeau’s message I looked up the bacteria he mentioned that causes fecal breath. I am going to try this test and see if I can get a resolution to this miserable health issue.
https://www.perioimplantadvisory.com/clinical-tips/article/55131135/bad-breath-caused-by-leaky-gut-nutrition-may-help-both-problems