My gfs birth control pills have made her periods consistent & always on time for the past 5 years. why did her most recent period turn out to be just light spotting? we have never had sex, so she most likely cant be pregnant. she also has pcos.

It happens sometimes: Many women have occasional variation of their mucus discharge, some spotting between periods, a heavier period, a lighter period, or even a missed period. Having one or two of these symptoms doesn’t necessarily mean there is a medical problem, but a visit to one’s primary care or Ob-Gyn doctor is a good idea if symptoms are persistent, recurring, or worrisome.