Even technically pregnant until 3 weeks and you don't start producing hcg until then so could that be why my pregnancy test are negative?

Could be: You could get pregnant, but hormones that pregnancy test test for are after implantation and the body starts producing the hormone.

I don't understand: precisely what you are asking, but hCG is produced and detectable by 10-12 days after fertilization, which also means roughly 2-3 days before you'd expect your period in a 28-day cycle. If you test negative at this time, you are not pregnant. Hope this helps.