If you go to mymonthlycycles ******* and use their pregnancy calculator that will help you out. You can use a "Retro Calculator".
You would be about 17w4d if your due date is May 14th. That would also give you a conception window of August 20-30th with the most possible date being August 25th. Last menstrual period was probably in the ball park of August 10th.
well i am due may 12 and i know i conceived between august 21-24. i think it was the 22nd!