I'm 19 years old and have been on birth control for about five years now. My boyfriend and I have sex without a condom about five times a week, but he never ejaculates in me. There was one time about two weeks ago where he thought he may have a little bit, so I took a plan B pill. I take my pill between 8:30 and 9:30 every morning. This week I have no pills since it is a 21-day cycle. I normally get my period on tuesday night (last night) but have still not gotten it. I did not take the last pill of the 21-day cycle, so I thought it would show up a day earlier, but still nothing. I am also in University and in the middle of exams. Should I be worried about pregnancy?