Can I be pregnant?

Normal period falls on 20-21st. Had unprotected sex on 11th.Took I-pill within 12hrs. Next period came on 27th with shorter duration.On following month also period came on 31st with a duration of only one day. The discharge in both periods were minimum. I am worried if it is ok or not. Is there any chance of getting pregnant? I am 40yrs .Pls reply. I am tensed.

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