You clearly know your cat ailments! That was pretty much Dr. Jeff's conclusion, as well... so we're doing a urinary stress diet. The last month or so has been stressful due to numerous house guests; the adult kids visiting several times, and one of the Humans being away on business trips three times. After June 15th, things should settle down again... and life will be back to a routine. I'm a VERY sensitive cat...
=^..^=
Sadly, I have been there and done that with idiopathic cystitis and I know the signs. Keep stress levels down and the diet should help