Heck, if I understand you correctly you've had a dozen treatments over a period of about 6 months. Half of them MMC and half BCG. I recall how bad my reaction was to only 1 MMC instillation. Your bladder has been under serious attack, over a relatively short period, in an effort to stimulate an immune response or kill off cancer cells. I'd be surprised if there were not any red areas upon cystoscopic examination so soon after BCG treatments. Until another biopsy is done, there is no real way to know if these areas are cause for concern. Has the TURBT been scheduled yet?
Until then, drink water like it's your job. I can relate totally to the burning and pain, especially at the start and end of the stream. It hurts so much it makes me shake sometimes. Eventually, it gets easier. Everything changes with time. I hope for the best and believe that even the worst (RC) isn't so bad in the entire scheme of things. The wisest comment I've read to date: It's about saving my life, not necessarily my bladder.