It is not uncommon for the pill to suppress your periods especially once you are in the peri-menopausal range (anytime after 35). Your own body is producing much lower levels of estrogen and progesterone now tht you are 51, so the most likely explanation of the bleeding is that you have been very slowly building up a lining in your uterus (slowly because of the low estrogen) and now that lining is finally thick enough that you are beginning to shed it. Because it has been so long since you've bled, you do need to be evaluated by a doctor. Most likely, they will do a vaginal ultrasound to look at the thickness of the lining and possibly do a biopsy to assure that there is nothing abnormal causing the bleeding. Good luck and keep in touch, Sandy Greenquist, CNM Menopause Clinician