I used to get a lot of UTIs.

Switching to a saddle that fit (so I wasn't "sitting" on soft tissues or jamming and abrading them) and getting rid of chamois (again, not jamming anything into the soft tissues and, most importantly, not sitting on sopping wet fabric) solved it.

I have very wide sit-bones and sweat like crazy. My body cried out for proper support and quick-drying breathable thin fabric, so this was the solution for me. These days I can do a 50 or 60 mile ride with no chamois on an unpadded saddle and be happier than I used to be after doing a 20 mile ride with padded shorts on a padded saddle. (Brooks B67 saddle $105 and UnderArmour compression shorts $25)

If you can figure out the cause, you will find a solution. Everyone is unique. Don't be afraid to try something that seems counter-intuitive. Hang in there!