If im 12 weeks pregnant and my due date is march 21 when exactly did i conceive?

Between 6/23-7/3/12.: Assuming regular periods and correct dating of this pregnancy, your probable ovulation date was 6/28/2012 and insemination must have occurred within +/- 5 days from that point (sperm can survive up to five days in the female genital tract). Implantation should have taken place around 7/4/2012! best of luck.

Approx Jun 28: If you have normal regular cycles and ovulate on approximately day 14 of your cycle, conception most ikely occurred around june 28. This, of course, may vary with each individual.