If u give birth 23rd march but u have a 28-33 cycle would u count 38 weeks back to determine conception date ?

Conception: There is not enough specific information in your question to give you an accurate answer. But, there are a lot of tools on the web that allow you to get all of the answers yourself. Some of these are called conception calculators. I use this one: http://www.Babymed.Com/pregnancy-due-date-calculator.

Estimated date : Of conception for a due date of 3/23/2014 is june 30, 2013. It would be close to accurate if the first day of your LMP was june 16, 2013.