"Perimenopause, which is a normal transition for women, can cause irregular periods due to a normal shift of your hormones, estrogen and progesterone," Mysore says. It happens before menopause, and according to Harvard Health Publishing, on average, it can last three to four years, but in some cases, it can be a few months to as long as a decade. Some other symptoms include hot flashes and night sweats, vaginal dryness, uterine bleeding problems, sleep disturbances, and mood symptoms.