if you have a 28 day schedule, take the date of your last missed period and add 2 weeks to it... that will give you a general idea of your date of conception. if your schedule is not 28 days, take the # of days your cycle is and subtract 14 days and the remainder is the day you ovulated (30 day schedule: 30 days - 14 days = ovulated on day 16). then take the remainder and add that to your last missed period (for the 30 day schedule, add 16 days). sorry if it sounds confusing.