I Think I Have A Pinched Nerve In My Left

I think I have a pinched nerve in my left shoulder blade from sleeping wrong (slept on wrong pillow, causing neck strain). I have difficulty breathing where I feel like I have to take shallow breaths, with deep breaths hurting my left shoulder and left pectoral close to my sternum. I have weakness in my arms and feel fatigued with limited movement making me slightly out of breath. Should I be concerned?