How late should my period be before taking a pregnancy test? i took one the first day i missed my period which is today it was negative..im having cramps and my usual pms symptoms..i had intercourse on oct 2nd and 12th unprotected?

1 week late: Home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, vaginal spotting, or medications. A test is very accurate by 3 weeks after sex (3 weeks after when conception might have happened) or 1 week after missing a period. If done sooner, a negative result may be due to testing too early such as less than 2 weeks after conception.