I think I have IC now....and yes prob from a shit ton of treatments!!! Thanks for the smile!!!
You may wish to check out The ICA site : Interstitial Cystitis, IC, Bladder Pain, Urgency, Frequency, Hunner's Ulcers
They have a lot of good info, and there are now many good docs that treat. -- you may be able to get a referral through a good doc list or through a member near you. It is a nasty disease all by itself , and has degrees of severity just as ME/CFS. I spent a couple years sleeping on the floor of the Bathroom. Interesting that yours was triggered by Rituxan -- mine was triggered by alpha interferon. All immune stuff.
Hope you find a treatment to get that under control. Some things work better for some people. Well you've heard that before, eh? Best.