I had been having my period like clockwork on the 11h on every month, in August my husband & I had a bit of a birth control accident. So I took the plan B pill, my cycle started again the 22nd of that month in addition to having my period already on the 11th in August. In September my cycle stayed at the 22nd, but this month in October I have not gotten my period at all. I took a test, but it was negative. However, my first pregnancy I couldn't get a positive until I was 7 or 8 weeks along. I have heard the plan b pill messes up your cycle, but it's weird that I had my period in September the same day as whenever I had another's cycle in August. Should I be concerned that I am pregnant?