it's probably not a good idea to take supplements or BC pills during your fast.
regarding the heavy flow, try taking a tablespoon of blackstrap molasses* daily and chase it with 2 tablespoons of apple cider vinegar (the mother brand) in 10 oz of water daily. you will notice a significant difference in your menstruation...it will be lighter & less crampy.
try this of course when you're not fasting! : )
*blackstrap molasses is an ancient remedy & contains megadoses of iron, potassium & magnesium...helps with feminine issues and really works. i had a uterine fibroid and it definitely helped me when i had heavy menstrual cycles. the heavy flow disappeared after consuming the elixir for a month and then i shrunk the fibroid with water fasting. i hope to completely eliminate it with my final water fast.