I really need help. My due date is September 16th. My last period was December 12, 2011. I had sex that same day. It was a regular period. Lasted for about 5 days. I had sex with another person the 21st of December and continuously after that. When are my possible conception dates? On Feb 25th I had my first ultrasound and the GA measurement was 10w 5d... please help

Honestly it could be either partners. The measurement puts your conception date on the 12, and some babies grow faster, others slower and others right on time. The only way you'll be able to know who the father is is to get a DNA test.

It seems to me it was the first guy

But then its too close to tell best to get a dna test for piece of mind I'm so sorry your in this situation hang in there :)

There is no way to be that exact on finding conception dates, You will have to wait till the child is born and do a DNA test

It is more than likely the second guy. Check out a fertility calendar / calculator. You will find that you are more than likely not fertile the day you start your period.

Wow, I have a similar situation... did the doctor ever give you a estimated conception date? My ex due date was sept.3, changed to sept 17 due to her measuring 2 weeks behind... estimated conception date nov. 29, the second day of her period.