Had sex with wife. her period is late by alomst 3 weeks.did the pregnancy test 7 times and all were negative. any chance of pregnancy?

No, not likely: Home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses, sexually transmitted diseases, vaginal spotting, or medications. A test gives a reliable result 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.