Hi,I am 28 yrs old.my usual date pf periods is 5-7 days more than the date on which d period came the previous month.that means I have a cycle of 35-37 days.my last period starting date was feb9th 2009.I had sex after my period about 3 times in feb,then I have had sex around 5 times in march 2009 till date(24th march) .I have not got my period yet.if I have conceived,how do I know if it was in feb or in march!?

Your doctor should be able to give you a date with an ultra sound judging by the development of the fetus. It won't bee 100% accurate to the day but they are usually pretty good :)

IF you are pregnant, and that's a big IF, according to my handy dandy gestational wheel I use at work, the same one's the doctors use, you would have conceived on or around February 23.

Since your period is obviously late, have you tried taking a HPT using first morning urine?

The earlier you get an ultrasound the more accurate it is.. I think around 13 weeks is when they start really developing at their own rate