How do I know if plan B worked?

Patient: I decided I wanted my period to start a week earlier than normal, after my second row of pills I stopped taking them. On the last day that I took them, I had unprotected sex which worried me so I took plan B approximately 16hrs after. It has been 4 days and my period still hasn’t come. Should I be worried?

Symptoms: Nausea, lower abdomen cramping

Doctor: HelloThanks for the queryYour periods have not yet come due to the sudden stop in birth control pills, and also taki ng plan B after having an intercourse, which is also hormonal.This would surely cause changes in the menstrual cycle.Since plan B was taken on time, you need to worry much about the chances of getting pregnant.Wait for a week to get your cycles, in case you don’t then you do a urine pregnancy test to confirm the pregnancyHope this helped.Regards