Understanding Your Due Date: Resolving Conception Date Discrepancies

Question
my due date is may 26,06 so which means i am 37 weeks. my last period was aug 1 or 2nd and lasted until the 5th. i calculated the date from my last period and it says august 15 was my conception date. i dont understand from ultrasound how i can only be 37 weeks...my period isnt always regular so im really confused on when i concieved. can you help me understand this whole calculation?

Answer
Are you absolutely certain that your last period was August 1, 2005.  Because if it was, than you should be 39 weeks and 6 days.  However, if an ultrasound indicated that you are only 37 weeks, your Dr. may have adjusted your due date due to the size and maturity of the baby.  You would have conceived about 10-15 days after the date of your last menstraul period.