When was your last menstrual cycle.? What you do is take your last menstrual cycle and add 40 weeks to that. You will then know your due date, and also how many weeks you are from your last period, is how far along you are. But just coming from you saying you conceived on Dec. 7ths. I would say you are about 6 almost 7 weeks pregnant.
Due August 31st, 6w5d along :) were you tracking your ovulation or was that just the day you had sex? Cause sperm can live 5-7 days in the vagina so, if you had sex the 7th, you may have gotten pregnant anywhere from the 7th- 14th. Always best to give the first dying of your last period.
I got preg the 6 and am 7 weeks today. My due date is aug 29. But I know I ovulated that day so knowing your lmp helps alot and when you ovulate.