Moinegirl

You start bleeding when your hormones drop.  For example, when you stop taking the pill, that's a drop in hormones, and a few days later, voila, there's your period.  Changing your diet - adding more fat, having a better ratio of carbs/fat/protein, eating less processed food - whether it's Whole30 or not - can have the same effect.  Even though you're on the pill, your body is still making hormones.  As hormones adjust, they can rise and fall, triggering a bleed.  Some people can pinpoint a certain food group or beverage, but for many, it's the overall effect.