OK I had sex with a friend the second week or the thir week of November 2007 and I got back with my boyfriend December and we had sex December 14 through the 16th my period came on December 2,2007 and my estimate due date was September 7 2008 but the ultra sound due date was September 5, 2008 and I had my daughter September 3, 2008 so woukd the baby be my boyfriend or my friend?

It is impossible to say whose baby it is without a paternity test. If the first day of your period was indeed on December 2, you most likely conceived on December 16. That is just an estimate though.

I agree. If you had a period Dec 2, then you most likely conceived around the 14th of December and the baby would be your boyfriend's.

The difference between sept 3, 5, 7 is insignificant. These are all practically the same date. Babies are not all born the exact number of days after conception, so even if you knew the exact day of conception, you could not predict the due with perfect certainty.