When is the soonest i can take a pregnancy test, after i (think) had implatation bleeding?

Missed period.: You can take a standard home pregnancy test as soon as you miss your period. It is best to use the first morning void.

Forget implantation: Bleeding, it's unreliable and usually doesn't happen. If you know when you ovulated you can test 11-12 days after that, if you don't know ovulation you can test 1-2 days before your next expected period.