My last period what may 3 and i am pregnant my cycles come around the same time each month in april it came around the 5th. i have been trying to calculate my conception date but don't quite understand how to. at an 8wk check up i had an ultrasound and sh

2/7/13: On reg periods, which it sounds like you have, you can expect to ovulate about 2 weeks before your next period starts.

Naegele's rule: You need to know the first day of your last period (the lmp). Use this formula: example: if your LMP was 5 april 2012 add 1 year equals 5 april 2013 subtract 3 months equals 5 january 2013 add 7 days equals your edc (due date) 12 january 2013 from wikipedia.