emergency contraception
"I took Plan B 26 hours later just in case. I felt a little nausea and had a headache about two hours after taking it so I went to sleep. Two days later I got my period. I can't really tell if it was early or late because my period has always been erratic, but I was happy to get it. 
My advice is do not take this pill very often because it is not designed for frequent use because of the high dosage. Get on regular birth control and avoid mistakes. 
Overall my experience was good, symptoms are not very severe and went away quickly."