Hi, I'm 16 years old and my period is known to be heavy and irregular, I had my period from around December 17th or 19th to the 24th. Since then I have not gotten my period. On January 30th my boyfriend and I had sex, we used protection but the condom broke and as soon as it did he pulled out. We had sex again on February 6th and same thing happened. I went to the doctors yesterday and my doctor prescribed me "plan b". During the whole month of January I was intensely stressed out with work school, my mother pushing me to take the SAT's and so on so I don't know if that would have thrown me off or what but I am freaking out . If anyone knows how long plan b takes to work I'd like to know.