How can you be 5 weeks and 3 days pregnant on May 28 if the baby was conceived 3?

It is not possible to be 5 weeks and 3 days pregnant on May 28 if the baby was conceived on March 3. Pregnancy is calculated from the first day of the last menstrual period, not from the date of conception. The average menstrual cycle is 28 days, so 5 weeks and 3 days from March 3 would be April 10, not May 28.