It's depends how often you have sexual intercourse. If you have intercourse very frequently then you should wait for missing a period. Only after that you should go for beta HCG level test. If you have intercourse once in a month or even less frequently  and you have irregular periods (like once in 40-50-60 days) then you should get your beta HCG level done three weeks after the intercourse.

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If you have an irregular period then do a pregnancy test after 1 week of the longest period length you have ever had Eg if you had 2 months as your longest period till now then do test after 2 months plus 1wk

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12 days after intercourse

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Irrespective of the date of intercourse you can go for a pregnancy test on day 37 counting from day one of the periods

2 weeks

After 3 weeks.

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