By: Tammy McCarrus, M.D. Irregular Menstrual Cycles/Uterine Bleeding Q: What causes long or irregular periods? A: Periods can be longer than average for many reasons, including hormonal imbalances due to irregular or skipped ovulation, medications you are taking, weight changes (both up and down), stress, problems with the cervix and uterine growths like fibroids. Missed [...]