I was supposed to start my period yesterday and still no sign of it other than some light cramping in my upper abdominal region and pelvis area. I took Plan B earlier in the month but had sex about 6 times unprotected since then using the pull out method which was successful each time. Today I checked my cervical mucus and it was like egg whites as if I were ovulating. Other than the possibility of being pregnant (which were fine with of it happens), are there any other possible explanations for this?