Hi.. im 21 weeks pregnant and 5month i was trying to figure out when did i get pregnant date due january 15?

Can subtract 2 weeks: If at 21-weeks, subtract 2 weeks from the number of "weeks pregnant" and the answer reveals the estimated conception date. That is because the standard way of counting pregnancy weeks sets 0-weeks as the first day of the last menstrual period. That means 2-weeks is usually ovulation and conception. So, 6-weeks pregnant equals 4 weeks after conception. Using a calendar and counting backwards helps.