Where did you order the binder and what model did you get? My boyfriend's rather large on the chest and he finds that the Underworks Tritop works best for him.
If this is your first binder, it's possible that you actually have the right size and still can't get it on. If your hips aren't much bigger than your shoulders/chest you might want to try to turn it inside out and 'step into it'. Top side down, pull it over your hips and then pull the top side over the bottom side (so it slides over itself and turns back right side out). If all goes well you just have to force the straps over your arms now.
My boyfriend has too much trouble with that way, but I prefer it over the feeling in my shoulders and everything when I try and force it over my head. I mean, it works, but I rather not.
