Levonorgestrel
"on March 21-25 I had my period. On March 26 I had an accident. My cycle ranges from 28-33 days. I took plan B within 1 hour that same day March 26. That day I got cramps and got really tired. The next day I experienced diahrrea. On March 31st I started bleeding again which scared me and it lasted 4 days. The bleeding was really light. I spent all April worrying.  I took over 10 home pregnancy test and they were all negative. Well today I started bleeding again which makes me 3 days late from my actual period. Yet on time from the plan B period. I never want to go through this ever again."