HBT - have been having bladder pain and pelvic floor problems the past year which the docs (GP and gynae) suspect is IC. (I refuse to have the general anaesthetic just to confirm my diagnosis as I am pretty confident this is what mine is as I only suffer when I eat certain foods). My attacks last up to 10 days unfortunately. They start with pain in my urethra and after a day or so the whole bladder is heavy and with spasm.
My problem was triggered one day about a year ago by drinking 2 tall glasses of orange and grapefruit juice at a friends house, along with a couple glasses white wine. I awoke the next morning with excrutiating sharp pains in my bladder and pelvic floor pain that went on for several weeks. I was tested and no infection present. It seems this bad episode finally broke down my bladder lining. Previously OJ would set me off with urethra pain for 2-3 days about 50% of the time that I drank it and cooking with sherry would do the same but that was nothing and very liveable with compared to now. Since this happened, I cannot tolerate most fruit and anything with citric acid in it at all and this includes all jams, fruit drinks, canned fruits etc.. I can't have tomatoes or bell peppers. I can't drink wine or even beer or soft drinks as the acid in those seems to set me off. Even sparkling water

. No tea or coffee or dark chocolate. No spicy foods. I am still working my way through what I can eat - so far most fruits are out, although fresh apples and pears seem fine and cooked fruits in some (calorie filled) hot stodgy puddings are sometimes OK. I cannot tolerate any pickles which i used to love, nohing containing lemon juice. Bananas - just a couple of fresh slices cause me agony but I can eat calorie laden banana bread! It's a nightmare when you are trying to lose weight!
I'm still trying to build up what I can eat...I found the other day I could eat Italian pizza if I just have a small amount with something else bland as my main dish (eg some cheesy pasta) as the small amount of tomato is cooked and weakened by the blander foods. I seem to be able to tolerate a very small amount of baked beans on a baked potato too. Again - the key is it is cooked and so less acidic.
I find I get temporary relief occasionally from a flare from a teaspoon of sodium bicarbonate in water, but it doesn't last long.
I wonder - have you spoken to Joliejacq (JJ) about this? She has had IC for years and has been a lifesaver to me when i felt i was going to go insane! She has posted several times about it. She has some great tips such as sitting on a hot water bottle and drinking lots of water etc.