My boyfriend and I had sex for the first time in the beginning of September right as my period was ending (the last day). I got my period two weeks after that, which means it was 2 weeks early. It was a regular period (heavy and dark). Now a month later, my period was scheduled to come four days ago and it hasn't come yet. Is this normal? We haven't had sex since then and he used protection, even pulled out way before he came. Should I be concerned?