thanks for using health care magic.
pills act by various mechanisms such as preventing ovulation and fertilization and by increasing the cervical plug to prevent the entrance of sperms.
Haven taken the emergency contraceptive pill one hour prior to intercourse, it is less likely to have had a pregnancy
given the above mechanisms and that emergency pills protects against pregnant if taken for up to 72 hours after intercourse.
The absence of menses is likely a side effect of the pill which causes hormonal
imbalance. However, though its less likely you could be pregnant, you should re do the pregnancy test in a week's time.