Levonorgestrel
"I had a incident on 11/26/14, so that same morning 11/27 I went and got a Plan B, that same day symptoms kicked in hard headache, Severe nausea and cramps and its still going on because today I started bleeding 12/5 and my period always come at the end of the month. I guess this is just confirmation that the pill work and I will still get my period around the end of December."