Hello,
Welcome to ehealthforum and thanks for writing
I pill is an emergency contraceptive pill and is effective for pregnancy prevention only if taken within 72 hours of sexual contact and only for one session and not consecutive sessions performed regularly.Since it is high dose hormonal pill it is not recommended for regular use and should be taken only during emergency conditions.
If you had intercourse during ovulation period then chances of pregnancy are present.It can cause side effects as withdrawl bleeding,spotting and delayed next periods so chances are there that you might be exhibiting that even.
Wait for a week from the expected period date and if the periods do not start then get a Urine test done for pregnancy determination and consider visiting a Gynaecologist for evaluation.
Take care!