An important note is to gingerly lift your head. You do not want to be lifting your shoulders at all. It is a very slight motion of lifting only the head. If you lift your head/shoulders too far, it will give you a false measurement of your gap, as it brings your rectus abdominis closer together. Simply lift your head just until you feel slight movement in your abdominal muscles.
Here is an overview on diastasis recti, written instructions on how to assess, and ways you can start improving the condition. This PDF is two pages, so be sure to hit the “flip page” button on the bottom left.Diastasis-Recti-By-Diana-Fassett_Blog-1