If she concieved around june 7th... The baby's due date would be at the end of february..
She would have had to concieve around the middle of july 2005 to have a baby due in april, 2006. I only know this because my due date is april 6th. This is of course if the baby made it to full term.
If you werent having sex with her after june 7th, then chances are, this baby isnt yours, unless the baby came out a month and a half pre-mature.