Hi there, I have understood your concern. I will suggest you the best possible treatment options.
1 ) First of all do not panic.
2 ) As per your history, you have regularly used birth control pills, and finished the pills on 12th March. And on 13th March there was episode of unprotected sex act.
3 ) In such case, I will suggest you not to worry about the
pregnancy. As previously taken birth control pills have already worked to prevent the egg formation and you were in safe period.
4 ) If you do not get your periods within 3 to 10 days of finishing the pills, then you need to get morning's first sample of urine tested for pregnancy.
In case of doubt blood
beta HCG test and USG will be of help.
5 ) please get proper sex
counselling done. Use of suitable
contraceptive method will help you to prevent the unwanted pregnancy and will help you to enjoy the sex life.
I hope this answer helps you.
Thanks.
Dr. Purushottam Neurgaonkar.