I was diagnosed with interstitial cystitis about two years ago. As it turned out, I was actually misdiagnosed. What I had were three kidney stones imbedded in my right ureter. It was 5 agonizing weeks before I had surgery to remove them. During that time I had all the symptoms of cystitis--it was the worst thing I've ever had to endure.
One thing that helped me out was drinking herb teas with demulcent (mucilaginous/soothing) properties. These included cornsilk, marshmellow root, couchgrass, and slippery elm. These are all good for treating an inflamed urinary tract. Mix equal parts of them and brew into a tea--use about 2 T of the mixture per teacup. Another remedy that seemed to help me was a barley water concoction. Mix 2 cups barley and about1 quart(?) water. Simmer until the liquid is reduced by half. Squeeze a little lemon zest in too. Drink the watery part and throw away the barley. I used to keep a lot of this stuff around and sip on it all day long. Also, as you know, drink lots of water with IC, and stay away from any irritating foods--some women with this condition have found relief by switching to a complete vegetarian diet. My doctor told me that while vitamin C is good for killing bacteria, it also can irritate a sensitive bladder. "Like putting salt on a wound" were his words. I'd stay away from vitamin C in the ascorbic acid form as that can be the most irritating. Talk to someone at your local health food store about a non-irritating form of C --if one exists. Last thing--I found lots of information about IC on the web.
Good luck and don't give up hope.