Levonorgestrel
"Already posted about my side effects from the pill but that was before I got my period so I wanted to share the rest of my experience. Did not get my period until exactly 1 month after taking plan b. Had a terrible headache and nausea all day, which isn't a common PMS thing for me. It was 2 weeks late! I know it's hard but don't stress, it will do weird things to your body. Good luck!!"