My LMP Was about March 20, 2011 . I am 28 Weeks and 5 Days Pregnant , I'm due on December 25,2011 . Is there any possibility that I conceived on April 15 2011 ?

The week and day guess is just that a prediction, based on estimates given to the doctor or size of the fetus using ultra sounds. So it sounds like that could be a good date.

Well I got my first Ultra Sound on May 16th , 2011 . It showed that I was 8 Weeks and 1 day Pregnant . I asked my doctor if there's any possibility I could have conceived on April 15 and she said that it's not likely.