pills are meant to be used once or twice per year for the real emergencies and are not to be considered a replacement for regular contraception
. You are lucky not to have gross hormone imbalances; these pills are known to cause severe hormone disturbances in many users leading to fertility
problems in future. So long as you continue to have regular ovulatory cycles, you need not worry about the reduced flow. Slight variations often do happen with increasing age. Please have a proper gynecological evaluation if you suspect hormone imbalance. Hope this helps.