I was born at Ft Belvoir and need to get my Birth certificate how do I do that

Still live in Virginia? Go to DMV and they can print one right there.

You need to go to records, that is located in the basement. And present your military i d if you have one, or call and ask for the phone number for records. And then call them up and ask them what you need to bring to verify that you are who you are that way you can get a copy of your birth certificate.