My due date is dec 27 . Can someone tell when I got pregnant please

How do you count when you got pregnant by using you duedate?

Go back nine months then consider the date of conception any time from two weeks before that date to two weeks after that date.

Yes that means there is an entire month it might have happened. Current medical science can not be more specific than that.

If this is a question of paternity because there's more than one possible father, there's no way to go by your due date. You'll have to wait until the baby is born and do a DNA test for all potential fathers.