I too started douching w/ peroxide and vinegar due to a stubborn yeast infection and- voila!! IC symptoms (burning, pressure, pain, frequency) were soooo much better. So I douched for about 2 months, but it kept coming back quickly unless I douched every few hours. I learned I have a very heavy growth of group B strep in my vagina (tested negative for it 3 years ago, before IC started). So this explains why antibiotics always made my bladder feel better, but after I stopped i'd get a major flare-up (good bacteria killed off enabled bad ones to proliferate more).
Currently having luck with boric acid. I insert a "00" size veggie cap full of it at least once a day, and also a cap full of kefir cultured milk to repopulate good bacteria.