I'm 16 years old, I don't take birth control and I've never taken a Plan B pill. My usual menstrual cycle is 7 days long on the last week of the month, and it is usually very heavy bleeding. This month I got my period 2 weeks early, on November 11, and it only lasted 5 days. Yesterday, November 23, I started bleeding again heavily. I took a pregnancy test and it was negative, so what is going on?