If hcg isn't produced until 7-10 post conception, why do some dr's say that u can test positive (if pregnant) just 3days post conception? who's right?

Wrong: Traditional pregnancy test that measures HCG is not positive three days after fertilization.

Impossible: You may have possibly have a positive pregnancy test as early as 3 days after implantation. It takes almost a week from conception till implantation. The HCG which is what the pregnancy test is measuring isn't even released until after implantation.