My due date is dec 10th and i have irregular periods but i had sex on mar 8th and mar 19th. is there a way i would know which date is my conception date?

Can only estimate: Dates are just estimates, and a few days or a week does not make any difference in almost all cases. One can just get a calendar and count backwards 38 weeks from the estimated due date (38 weeks back from Dec. 10) to see the estimated conception date. The exact conception date of a natural pregnancy is never known because nobody can tell when the sperm entered the egg.