Q: When does the HPT become positive?
A: The hCG level in the blood and the urine depend on when the fertilized egg implants. Most sensitive current pregnancy test kits (sensitivity 25 mIU/ml) can detect the pregnancy hormone hCG in the urine as early as 3-4 days after implantation, though it sometimes can take longer. Because implantation happens on average 6-12 days after ovulation, the urine pregnancy test may not become positive until 16-17 days after ovulation.
If AF hasn't come by that time, and the HPT remains negative, then you may want to ask your doctor to do a blood hCG test.