Its not a false negative...its negative at that time because you're not pregnant at that time. Most women who find out they're pregnant would get a negative at 8dpo because at that point you would have to have the egg implanted at 6dpo for it to show on a test at 8dpo. (That's around 5% of pregnancies that do that). Wait. Retest in 3-4 days

It takes 6-12 days to implant. That's why most women are concerned when they find out their baby isn't as far along as they thought based on their LMP.