If his date was determined by an early scan you probably conceived sometime around 11 May 2004 give or take 4 days. If however he was born on 3 Feb as a term baby and you had no scans the conception date could be out by 3 weeks.
May 9-13
due date october 5
Around the middle of February. You usually take your due date and go backwards nine months and two week for an approximate date.
feb 3
The approximate date of conception was June 10th
July 3
Wednesday, Oct. 3, 2007
Thursday 11th October, roughly
Roughly Tuesday 10th June 2008
Roughly Friday July 11th 2008
Roughly Friday December 25th 2009
March 3rd 2009? Then your due date would be roughly Tuesday December 8th 2009