<s>[INST] I had my cycle on May 1st, I have a 30 day regular cycle. I had intercourse on May 9, but he did not ejaculate in me. I then had sex on May 14th and 17th when he did ejaculate inside. When I had my first ultrasound, the physicians office confirmed a due date of February 6th, 2011. In your opinion, which day did I conceive? [/INST] Hello,Physicians calculate according to your last menstrual period (LMP) then add 9 months plus 7 days to calculate the date. But if you have a regular cycle, you say your LMP is 30 May then around 14 to 17 you might ovulate and have sex during that time. Most likely it's on 14th day rupture if cycle is of 28 days. You have to check by USG rupture.Hope I have answered your query. Let me know if I can assist you further.Regards,Dr. Sheetal Agarwal </s>