Hi! just wanna know when is my possible conception days cos i had sex on the 17th of Dec and 10th of January . Had my internal ultrasound on the 25th of January and found out i am 6weeks 1 day gestational sac . yolk sac present but no fetal pole noted . LMP was Dec11 . When i had again my ultrasound Feb 1, it put me back at crl measured 6 weeks 3 days with 143 heartbeat . Did it take a long implantation if I concvd in Dec ? And if I concvd in January, is it possible to see gestational sac and yolk sac 2 weeks after conception?