I assume each UTI has been accompanied by a lab test and a list of susceptibilities to guide the antibiotics used. Also if it hasn't been done, request your urologist to do a flex-cysto to check the urethra and bladder for problems - it's easy, quick and painless.
"cranberry" contains d-mannose, obtainable in powder form on ebay. google for methods/amounts to take for preventive or when you think it may be starting. Generally preventive is about 1.5g 2xday, very early onset is 5 days of 1.5g every 2-3 hrs while awake. When it's full blown you need antibiotics.
Assure no self contamination, either by hygiene or by vulva /pelvic shape eg area around urethra.
Consider lactobacillus health in vagina vs sex, lubricants, dilation, douche, etc.
I just started experiencing this slowly increasing from 15 years ago but now every 2-3 weeks. I am due for a labia resection on Mon in hopes that will help prevent it from coming back.
Since I am between full blown UTIs I am doing the d-mannose thing and it seems to hold leukocytes (Siemens strips) to a minimum and symptoms to zero, but only on day 2 of the intense (of 5) and was sloppy today.