Which pregnancy test says 2-3 weeks? You have to mention this to get most accurate answer. Anyhow, pregnancy is counted from the first day of last menstrual period. And first test of pregnancy is done after missing of periods, so, test at this time means 4 weeks pregnancy if pregnant. So, if your any test is saying 3 weeks pregnant then it might be from day of conception. To know this day of conception, add 2 weeks in the first day of last menstrual period. Day of intercourse does not mean day of pregnancy. Because an intercourse 3-4 days before ovulation can also cause pregnancy.