I didn't know you had pain. That sounds more like interstitial cystitis, my cat has that where it is called FIC. You can now tell people you were diagnosed by someone on the Internet because their cat had it. No, I'm kidding, I know that's nuts and of course no one can diagnose here.

Cats with this, have a problem with the lining of their bladder. This is worsened by stress. In both cats and humans it can get worse by eating certain foods. My cat needs a daily replacement to help build up the bladder lining. It is probably but not proven to be autoimmune. In cats, they are encouraged to drink more water, because they actually realize, just like people, that drinking water causes peeing which they dislike. Drinking too little water can further hurt the bladder. In humans this translates into drinking water, not tea, coffee or sodas. My cat is totally dependent on glycosaminoglycan, which here is just a replacement and needs no prescription.

I would be very surprised if this is not used in the human form, since cats and humans actually have a very similar bladder.

In cats it is just guesswork, in humans they can go inside the bladder and look. But even then it can actually be hard to diagnose.

Take this for what it is, a story about my cat.