How early it to early to tell if you are pregnant?

It takes roughly 24 hours for sperm to travel to the egg & fertilize it & then another week or so for the fertilized egg to travel to the uterus & implant in the uterine wall. Once implanted, it begins to form the placenta, which is what produces HCG, the hormone that pregnancy tests look for, even the bloodtest that you get at the doctor's office.