After the egg and sperm meet, there is up to 6 days before they implant on the uterus wall. There is no way a test could be positive before implantation because, until implantation, your body will not know it is pregnant and will not produce hcg.

Pregnancy can be detected up to 4 days before your missed period. That doesn't always work and most women don't find out they are pregnant until their period is either due or late.

Good luck to you.