Hey, carabear! I'm so sorry to hear you're dealing with chronic, recurrent UTIs. I can certainly relate - I got my first UTI when I was maybe 8 or 9 and then around the same time I experienced my first signs of endometriosis, the UTIs spiraled out of control (about once a month, too). I had experienced enough UTIs in my lifetime where I felt confident that if it felt like I had one, I should actually have one. However, half the time, I would go to urgent care or take a UTI strip test from Walgreens and both would confirm the presence of leukocytes but not nitrites...no UTI.
What I have come to learn is that leukocytes can simply indicate is inflammation (which can often be representative of an infection, but not necessarily). The nitrites on the test strip indicate organism presence so an actual infection. My OBGYN and urologist don't think I have endo on my bladder, but believe there is something else at play here:
Recurrent UTIs can lead to something called Irritated Bladder Syndrome - when you have a flare up, your symptoms will mimic a UTI, but are already just irritation/inflammation
When I have this happen, I always use the test strips to eliminate whether it's an actual UTI. I drink a qt of water with AZO pain relief, use the heating pad, and try to ease up on things that could irritate my already p'oed bladder like coffee, alcohol, sex. In most case, the symptoms subside within 24 hours.