Hi Zanne, I’m sorry I can’t offer any help with what it could possibly be, but I hope you feel better soon. Do you get any relief sitting in a steaming hot bath? Just for temporary relief?
By flank pain, do you mean the area right at the top of your legs near your groin? I used to get intense pain there around that time of the month, so awful I had to sit down to stop it from hurting, I never understood the pain. Also when my crohn’s has been punishing me I get the same pain.