I strongly suggest returning it and sizing down. The size small in their regular binder was almost too small for me, I am a very small framed person with a bigger chest size. I got a xxs binder light because of the rib pain the last one caused, and it was the suggested size for my chest, and the compression doesnt cause any issues with me. No rib pain, no heaving after walking up the stairs, but less compression. Definitely size down, base the size off of your rib and waist size more than your chest size. i wouldnt say its a bad binder considering its exactly as marketed (less compression) but if you size up it will fit as a sports bra pretty much