The first day of my last period was 1/14/12 my due date is October 21,2012 how can I tell the day I got pregnant because there is two possibilities of who the father might be and it has really been bothering me can you help me please? :/

Once the baby is born you do a DNA test to decide who the father is, There is no way to pick for sure an exact date. How close together is the sex, if there is 3 weeks an estimated guess will be easier, if they are a week or even two apart, there is no way to know till a DNA test is done