If my conception date based on 6 week u/s is march 6 how likely did i get pregnant from sex on feb 24?

Very: With an ultrasound date of March 6 for conception, you could have gotten pregnant from sex any time from Feb. 20 to to Feb. 24 . Since the early stages of pregnancy are quite orderly & predictable, six week ultrasounds are remarkably accurate in estimating the date of conception.

If I understand the?: properly, it sounds like the US you had suggested that conception occurred on or near the 6th of March. If that's the case, sex on the 24th of Feb would be the outer limit of when conception can occcur. assuming you ovulated on the 3rd of March and the ovum was fertilized by sperm that had been present for 7 days, this is unlikely but theorethically possible. Sex after 24th more likely 2B source.