Hi Nitika, Welcome to HealthcareMagic Forum.
You have had sex on the 21st day of your Cycle. The best fertile Period to have Unprotected sex to be able to conceive is between the 10th and 20th day of your Cycle. You will have chances to conceive but very less. Wait for your next periods, if you happen to miss them, get a Urine Pregnancy
Test done using a early morning Urine sample after a week of missing your Periods. If you get your Periods, have alternate day Unprotected sex between the 10th and 20th day of your Cycle.