Not sure where you are on this "journey," but I've just completed #5. I also have Fibromyalgia, Psoriatic Arthritis, Severe Small-Fiber Neuropathy and Chronic Migraine. For the first 4 treatments, all I had was some burning, and some increase in the chronic fatigue. Yesterday's treatment is hitting harder, with nausea, mild low-grade fever, chills and hot flushes.
It's doable. I've re-adjusted my work schedule so that I'm working 3 long days, Mon-Wed, then treatments on Thursday. This has worked out well and I haven't missed work. Yes, today is not a great day, but I'm playing the long game here and my goal is bladder conservation. I will complete my 6th treatment in a week, then the follow up cystoscopy on Sept. 6th. After that, I have made it clear that I want to continue with maintenance for 3 years, and my doc agrees.
Every journey is different. I am an aggressive, pushy broad whose first response to the diagnosis was severe annoyance. I went from my first symptom to surgery in 9 days. That's how I roll.
The numbers are in your favor; do the reading and see that the goal here is to keep ahead of it, and that is doable. By putting up with the BCG (again, not fun but pretty easily endured) you improve your odds of reducing the likelihood of recurrence, and if the cancer does recur, reducing the advancement of Stage. Basically, do the BCG, significantly increase the likelihood that you will keep your bladder.