Is a 12 day period with heavy bleeding normal?

No. Stressful times?: Sometimes events in our lives or the lives of our family and friends can affect our cycles. Perhaps seasonal events, like at school, can make a couple of periods irregular. If there is no history of stressful events but one of unusual bleeding, then a call for appointment with obgyn might be considered. At this point starting a "diary" showing date, events, time and amount of bleeding helps doctor.