I'm 6 weeks pregnant found out today so when did i consive?

About 4 weeks ago. : When we say you are 6 weeks, we are counting from the first day of your last period. Before we knew how everything worked, that was the only thing we could use. Now we understand that ovulation occurs two weeks later. Conception would occur at that time. To be precise, cycle day 1 is the first day of your period . Most women ovulate on cycle day 14. Your fertile days are cycle days 10-16.