thanks for your query.
It is normal to have altered bleeding and spotting with Postinor, as it is a hormone containing pill
Also, having sex just the day after your period has an almost zero possibility of resulting in pregnancy
With protected sex, again chance of pregnancy is low.
However, every contraceptive
has an intrinsic failure rate.
Please wait until 15th of April, and if you do not have a normal period by then, take a home urine pregnancy test.
Also ensure that all sexual activity till then is protected sex.