Answer:
If it has been over a year since your last normal menses, then this is called postmenopausal bleeding and needs immediate evaluation to make sure that you do not have uterine cancer, which sometimes presents with abnormal bleeding.
You should make an appointment to see your health care provider, who will assess if this is abnormal or just your hormone fluctuations. He or she might suggest a pelvic ultrasound and possible biopsy of the uterus.