I dont know the medical reason behind it, but a few years ago when I decided to quit the pill, it was several weeks after my last pack before I started a normal AF. I had spotting on and off, my doctor said it was because my body was use to getting the BC and the 'aid' in having a normal AF, and when it took it away..it was momentarily confused as to what to do. That's how she explained it to me, so that I could understand.

Good luck!!

Red