What Causes Delay In Period Despite Having Postinor Post Unprotected Sex?

I got my period on feb 15 until feb 21. Had unprotected sex on feb 22. Took postinor on feb 23. Had irregular weird spotting start on feb 28 and continue for about 4 more days. Now its march 19 and i havnt gotten my period. I have never been late in my life. Ive always gotten my period 3 days before the date of the previous month. Should i be worried? Was the spotting an early period? Or am i supposed to get my period the same time as usual..?