The chances of pregnancy
are less since you had sex during the safe period in which pregnancy can be avoided in a natural way.Though there are some failure rates but the use of unwanted 72 on alternate days have further decreased your chance of getting pregnant.
The pills does have side effects and have effect on hormonal
imbalance and the periods may get delayed or increased bleeding during the periods.
If you have doubt then you may have the blood pregnancy test done and sonography
to rule out pregnancy.