Kathy,

I have RSD/CRPS in my back and yes I have a lot of difficulty with being in any position. Mine is primarily in my upper back and from your post I am gathering that's what you are referring to also. For me, lying on my back is the worst. Sitting upright is also difficult. The best position for me is a semi-reclining position. I spend a lot of time in my recliner. As far as the breathing issues it is really difficult or me to answer because the RSD/CRPS is also in my chest wall and rib cage on both sides so I rarely take a deep breath--in fact I avoid it at all costs due to pain. Sorry I couldn't be any more help.
Cricket