emergency contraception
"I had unprotected sex and took this about 3 hours afterwards.  I was so scared for so long!  I had about two days of light bleeding a week before my period was supposed to come.  I was afraid it was implantation bleeding!  But it wasn't!  Hallelujah!!!  
The pill definitely mucked up my cycles for a while.  My next period didn't come for two months.  Anyway, if you are freaking out about the possibility of being pregnant, take a breath.  I know how scary it is.  It is absolutely terrifying.  But this pill works!  You are going to be ok!"