At the beginning of February, I had an abortion. After my procedure I started on my birth control again just like the doctor had told me. I was just finishing my third week of my pills when I had sex, to be safe I got the Plan B less than 24 hours later. I'm supposed to get my period for the first time since December this week, but haven't gotten it yet. I usually get it on the Wednesday and it ends on the Sunday. Is it possible that the Plan B and my birth control failed?