I'm not sure if the low grade bladder cancer would contribute to your fatigue, and it may just be a coincidence. My husband has afib and high blood pressure, and he gets very fatigued due to his blood pressure meds, one of which is also used for his afib (beta blocker?). Dr. is trying to change dosages, change time of day he takes the various meds, etc., to try to resolve the fatigue. (My husband isn't the one who's had bladder cancer; I am.)
I'm a little confused by your saying you had a cystectomy, and that your cancer has returned. Normally "cystectomy" means surgical removal of the bladder. Maybe what you had before was TURBT (removal of the tumors) or possibly you had a partial cystectomy, which I don't think is too common. In any case, I'm sorry to hear about the recurrence. CIS, carcinoma in situ, is often treated with BCG. CIS is generally considered a higher grade type of bladder cancer, so I'm puzzled by the report that you have "low grade cells" and that it's CIS. "Wait and see" is not usually suggested as an option for CIS, where BCG is highly recommended. On the other hand, "wait and see" rather than BCG for low grade papillary cancers sounds reasonable given your other medical conditions. Are you absolutely sure the Dr. said you had CIS? CIS is a flat type of tumor on the bladder surface, while papillary tumors stick out from the surface like little mushrooms or broccoli stalks.
I had BCG treatments because I had a recurrence of low grade papillary bladder cancer, and though I tolerated it well, not everyone does. BCG treatments can contribute temporarily to a feeling of fatigue, and to having flu-like symptoms, bladder discomfort and bleeding, etc.
Wishing you well as you face your various medical "woes" and now this recurrence of bladder cancer
Ann