Knowing my body, the fact I keep fit, and have always been tiny down there - I took the risk of buying size 1. And what a relief that I did! The fit is superb, but I will admit it can be a bit too wide when pulling it out. It hurts a little. Not in a -Ill never use this again kind of way, but definitely painful.
Theres my two cents. C-section mommas who work out and look after your bodies, do consider the size 1. The size difference could be all the world when it comes to being comfortable - particularly when it's time to remove it.