do we all get it??

ok so assuming everyine reading this is female, do we all get CM?? im 24 and have been getting CM since 13 prbly even before, and had never known wat it was until Glow. none has ever even mentioned something close to it, and im just wondering if its only a small amount of us girls that get it or mostly all? and if so, why doesnt anyone tell us or teach us?!!