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If you had done a pregnancy
test yesterday & is negative then please repeat the test after 1 week with a kit or you can do Beta Hcg
for pregnancy) along with the kit for confirmation.If the second test is also negative then you will need to consult a Gynaecologist to find the cause of the delay.If you had regular periods & you had unprotected sex one day before the date of your menses the chances of pregnancy are less;the delay could also be due to anxiety
so relax & repeat test after 1 week if you don't get menses.