due date is march 20 2013 when did I conceived?

Hi,
Welcome to ehealthforum,
The intercourse closer to your ovulation day would result in pregnancy. You are closer to your ovulation time after finishing with periods. If your due date (completion of 40 weeks of gestation) is known, then you can count back to know your probable conception date and current gestational age. If your due date is March 20th, 2013 (completion of 40 weeks of gestation), then your probable ovulation day would be around June 27th 2012, and your conception date would lie between June 23rd, 2012 to July 1st, 2012 (calculation based on regular menstrual cycles of 28-30 days). Ultrasound scan done for dating can also help with knowing your probable conception date. Visit your doctor/gynecologist for further assistance and clarification.
Take care.

Thank u so much. Yah my last period was on June 25 but who knows just thank u got getting back I feel ALOT. better so got pregent on jun 27 from ur point of view thank u so much I read on all this stuff calculation n all just didn't understand it thank u so much. One more ? So the doctor said yesterday I'm 3 n a half months so who d o u keep track on calendar how do you go by the weeks you count on 7 or just 5 days of the week . And I'm having a c section so I go by 9 months right