The earliest you can get a positive result on the most sensitive pregnancy tests is seven days after ovulation. Implantation needs to occur before hCG is produced, and that generally happens between 6-12 days post ovulation, usually by 10 days after. For this reason, it makes economical sense to wait until 10-12 days after ovulation, but even then a significant percentage of women who are pregnant will still show a negative result. Many people won't have a positive HPT until the first day of a missed period or even a few days later.
Think this makes more sense