I am confused on how doctors get the due dates. Something happened once on November 17th, 2009 and I was told that it takes a couple of days to concieve. My LMP was November 7thth, 2009 and I was told my due date should be August 14, 2010. I am confused because I thought that I should be pregnan for 9 monthsand that would be August 17th, 2010. Can you please help me? Is this correct?