Sorry to hear about your injury. In its way, there's nothing quite so painful, because the only way not to move the break is not to breathe (which does have it's own drawbacks...
)
I don't think either of my martial artsy sons has ever used anything like a chest protector or such. Time may be the only thing that is going to keep you from rebreaking this thing again. Might talk to a physical therapist or sports trainer...they may have some specialized equipment they use for such things.
Sympathies....
Springmom