Sorry if this is a terribly dumb question, but is it possible for a cpap to blow post-nasal drip into lungs? I'm trying to find out why I've been short of breath since I started cpap. Allergies have always been a problem. Thanks.

I started w/CPAP two months ago. My wife and kids have noticed I gasp for breath at the slightest exertion. My back and chest feel tight, like I can't get a complete breath. Is this common, and CPAP-related? Will it go away, or does it indicate incompatibility with machine or settings?