Cystitis with forgetfulness?

I've had a urinary tract infection for half a year, and neither my gynecologist nor my urologist can find the cause. A cystoscopy showed severe inflammation, but the urine culture showed no bacteria. I'm not feeling well, and what I and those around me have noticed is that I've become very forgetful and confused. I can no longer remember names that I actually know well. It's getting worse and worse. What other treatments or tests can I do? Where do I need to go? And antibiotics aren't helping, but that's clear, even if there are no bacteria found in my urine.