Two Weeks Of Ruined Underwear
I got my period when I was about 11 years old, and because I was too young to know much about hormonal birth control options I experienced really irregular cycles for the next few years.
This caused a lot of problems, seeing as my period would spring on me without warning
but the worst of it happened in my second year of highschool: I got my period for two weeks straight. I went through two really heavy flows, thankfully devoid of cramps, and totally baffled my doctor. Never found out why it happened, and six years later it hasn't happened again.