This has not a certain period because every woman has a different menstrual cycle. There are so many general theories u must come through in the answers given here, but one should keep in one’s mind that pregnancy can be occurred after having sex at any point. I know so many women they got pregnant after having sex right after their periods, some got a pregnant third or fourth day of their periods and some of them got pregnant on the tenth or 11th day from the first day of their periods. My point is that you cannot get a sure shot time frame from the general advice. You can be pregnant on any day between your two periods.
Monitor your cycle and as per your cycle days, try to calculate your ovulation start date and from this date, a week before and three to four days after the ovulation date is your general pregnancy frame.
