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You should nt have taken the pill.There would be no chances of pregnancy
if you have unprotected sex during periods.Moreover you had protected sex.
Anyways , taking emergency contraception pills like unwanted , ipill
can cause menstrual abnormalities like delayed periods or intermittent bleeding.You are experiencing side effects of the pill.So do not worry and wait till the bleeding comes down.
Please keep in mind that you should not use emergency contraception pills as monthly contraception or frequently.