The back/spine/ribs/shoulders are all connected through very complex ligaments and muscles. I've pulled muscles in my back before which made it difficult to breath. Sounds like you could use some relaxation as I bet you're tense which is probally making your chest tight. I've had anxiety before which totally felt like a pile of bricks on my chest. Try a hot bath, some bananas, chamomile tea and some lite activity and I bet you'll feel better!