What Causes Delay In Periods After Taking Unwanted72?

Hello sir, my last month periods occour on 16th july n after dat i had unprotected sex with my fiance and i ll take unwanted 72 in 30-40 hrs. Bt dis month my periods which due on 13-15th aug.doesn t come till date. N last day i again use unwanted 72 medicine.. i had slight pain in my abdom. Bt ny periods are nt come... plz suggest