Is there a big chance of a false negative on a blue dye pregnancy test? If your only 3 weeks pregnant?

When should your period have been? How are you supposing you are 3 weeks pregnant?

conception occurs (on average) at 2 weeks pregnant. this is 2 weeks after the start of your period. the fertilized egg doesn't implant until 5 days after conception. so almost at week 3. your body doesn't start making pregnancy horemones until the egg implants and you actually become pregnant.
so testing at 3 weeks pregnant means your body has been making horemones for 2 days. there is no way a home pregnancy test will detect the pregnancy.

So if you are counting from the first day of your missed period, wait a week or 2 and test again.

wait till you miss your period then retake

Zetajen is right on. Even with early read tests, that is still REALLY early if you are calculating your weeks correctly.

This is the fourth time you've asked this. Lots of women have already given you good advice. The answers won't change.