What Causes Delayed Periods After Taking I-pill Followed By Sex?

hello doctor! I am 21 years old, me and my boyfriend had sex on 31st January and i took I-Pill on that day after 2 hours. After taking I-pill there was no bleeding or spot. my period must come on 13 of February month, will my period come on time or it will be delay i am just worried why did i not have bleeding with in 7 or 8 days my last period time was on 13 January till 18 January i had sex on 31 January & i took I-pill on 31 January after 2 hours of having sex but i did not get any bleeding which we have after taking it after 7 to 8 days when can i have my period last time it was on 13 January to 18 January will i have it on 13 February. please tell me how much possibilities are there to get pregnant..