Using a Gestational calendar,if the first day of your last period was June 21 and you know you concieved on July 5, you would be 40 weeks on March 27.
If I Conceived July 5th What's My Due Date?
You just have to count back 3 months and add 7 days, this will be your anticipated date of delivery. Hope this helps, good luck, and congrats to you.