How Many Weeks Pregnant Am I - My Due Date Is May 26?

Pregnancy is calculated from first day of last menstrual period and you have not written this date in your question. According to information given by you if your expected date of delivery is 26/5/2009 then your possible date of conception can be 2 September, 2008 with few days up or down because ovulation usually takes place at mid of the cycle but some ladies can ovulate early and some late. After ovulation, egg can live for 24 hours while sperms inside female body can live for 5-6 days. It is not necessary to become pregnant on the day of sex.