Tomorrow (4/19/13) I will be 12 weeks pregnant, while I think I already know my answer I would like to double check with anyone who might know better than me. My last period was Jan 25, 2013 and my ovulation date according to the conception calender online was Feb 8th. Now I made a mistake and had slept with a man who wasn't my boyfriend on Feb 11th. When I count 12 weeks back I come up with Feb 1st and my coworker counts all the way back to Jan 25th. I was told you are most fertile a week after your period, which would be exactly Feb 1st... and if that is all correct then it is my boyfriends... but I was told there is that teeny tiny chance that it is not. Everyone I have spoken with has said it is in fact my boyfriends and not the other guys... is that correct?

You have to get DNA testing done... your conception date was the period two weeks before to two weeks after the date 9 months prior to your due date. And two weeks before to two weeks after.

The date of your period means nothing. Women do not ovulate on a predictable date without Basal temp chart being kept.

That means anyone you slept with that entire month might be the father.

Online apps for ovulation are useless. They are not at all accurate, and are just meant to be used for fun. In order to predict ovulation you have to take your basal temperature and track ovulation for at least 6 months.

In other words, you can't go by the app.

Due dates can be off up to two weeks either way, so there is a chance that this other man is the father. The only way to find out is a DNA test after the baby is born. Anything else is a guess, and not at all accurate when determining the conception date and paternity.

Good luck.