Yikes! I'd actually be more concerned with all that antibiotic use than I would be with the platelet count. Taking antibiotics like that could cause you to become resistant and eventually, they won't work at all. You can't just take an antibiotic for three days....it probably won't kill the infection and could cause an antibiotic-resistant strain.
I'd work on trying to prevent UTI's in the first place rather than having to treat them all the time. Do you actually have cultures done that are positive? I'm asking because I used to get what I thought were UTI's, but I really had Interstitial Cystitis which is not an infection, it's inflammation. Antibiotics do not work for that.
www.verywell.com/ways-to-prevent-urinary-tract-infections-3522648
www.prevention.com/health/how-prevent-utis