I was extremely hygienic but the smell was pretty much always there, and was often much worse shortly after using the toilet, even if I took a shower afterward. This does not seem to
same problem people have with a fishy smell, by the way
SO, the solution for me turned out to be straightforward: Avoid all foods containing animal products. No meat, eggs, or dairy, including any foods that have ingredients such as whey, milk solids, etc.