What Causes A Delayed Menstrual Period?

I have had an sinus problem for the past 2 or 3 weeks , I usually get my period 28 days apart on a Wednesday for the past 2/3 months. My period was due Wednesday it is now Friday . I haven t had sex in about 2 months and when I did , I used protection, and he did not eject / cum ... so i know that is not it . Could my sinuses be delaying my period ?