I am confused about when I conceived and what the due date of my baby is. My last period was May 25th, 2009 and lasted five days. Average cycle between periods unknown... I don't pay attention, I had sex on June 3rd and June 19th. My first ultrasound estimated that I was 13 weeks pregnant and my due date is March 21st 2010 according to my doctor. So when is the most likely day I conceived and why is this not adding up. Could I have ovulated late in the month close to my next period which would have been late June. Help..

Due dates are an educated guestimation of when you conceived and when you are due. Most often guessed by the dates you list of your menstrual cycle.

Is there a benefit to knowing exactly which night you conceived?

Yes, this would help determine the father... thanks for your help

This is the most often reason that we see this question asked.

The only way to accurately determine the father when there are multiple partners within one cycle is DNA. It's unfortunate to hear, especially since you are not going to have an answer for at least 10 months, with probably disturbing consequences in the meantime.

Do the right thing, a child is an eighteen plus year investment, obligation, don't just make a guess... no matter how educated that you feel it may be.

Good luck to you.