What Causes A Delayed Period, Stomach And Thigh Pain After Taking ECP's?

hello, i married and had sex on 3rd of feb and taken i pill as contraceptive. my period date is 17, but till now(21st) i have not got my periods , i m very worried should i need to consult doctor, we don't want baby right now, i have pain in my thighs and stomach which happens everytime before my periods , everytime i take pill,my periods are delayed by 2 or 3 days, for how much time i have to wait and then conult doctor, plz tell me and also is taking a emergency contraceptive pill two three times in a month harmful.plz tell me as soon as possible