I had sex twice 11 days before my due period and had sex the night before my due period.I got my period. Doctors dates say I got pregnant the night before I got my period because they go from first day of last period
Could I have got pregnant those two times I had sex 11 days before that period or would have I not got it at all.

You will have to wait until the baby is born to have a DNA test done to determine who is the biological father of the child.

Why do doctors date pregnancy as 40 weeks from first day of your last menstrual period? When you could possibly have fallen pregnant a couple of weeks before that period

Gestational dating is all Best Guess as it is impossible to determine the actual date of conception.