How early can you detect pregnancy?

Ashley

Hello everyone… my period is late by 9 days. There is a slim chance I could be pregnant, I had sex the day before my period was suppose to start. So 10 days. I have taken half a dozen pregnancy tests and they are all very negative. Not even a faint line or anything. Is there a chance I could be pregnant and the tests are not picking it up? I have been using First Response and Pregmate strips. Thank you…