I had unprotected sex on December 23rd 2011 more then once. I was due for my period on the 30th of Dec. My last menstruation was on Dec 2nd and I am usually a 28 day cycle. I still have not gotten my period. I took a pregnancy test on Jan 2nd and it showed negative for pregnancy. Is the test right, am I not pregnant? What else could be making my period late?