Okay, so I know you're not supposed to bind your chest with just whatever's around the house, but lately I've been doing that frequently because nothing else seems to work (sports bras, etc) and I can't afford a binder. Recently though, I've noticed that sometimes (especially after laying on my stomach) I'll get this really really sharp stabby pain in my chest and I can't breathe deeply for a moment if I can breathe at all. Could I have injured something?