Fist day of my last period was on November 15. I did not get my period in December , on February 4, 2014 I had an ultrasound done and was informed that I am 6 weeks and one day pregnant. I was told that my due date is September 29 2014.I has sex on November 30 th December 1,2,3,10,11,14,15,16,17,19,20,January 8,9,10,11,On December 23 & 30th I have cheated on my boyfriend Who is the father ? And on what day I got pregnant? And is it posible that utrasound estimate is wrong ? Please help

The ultrasound is not exact, I hope you were not given an impression it was to the exact day it can be off a week or two. Which of course still means that either men could be the father.

This is common and is why they have DNA test after the child is born.

I'm sorry you have put yourself in this predicament. There is no way to know who the father of the baby is until it is born and a DNA test is done. You will have to inform both men that they are potentially a father.