When did i conceive? my due date was november 20th -21st & i had my daughter on the 16th .. & can you get pregnant & still have a regular period?

Around February 27: If your due date was November 20, you conceived around February 27. How accurate this is depends on how the due date was figured. An ultrasound at 7-9 weeks can be accurate within 5 days. Ultrasound later can be 10 days to 3 weeks off. You won't have periods while pregnant, though sometimes pregnancy related bleeding can confuse. Best wishes!