Pain under arm when breathing in?

For three days now I have had this horrible pain that is just below my arm-pit on the right side, when I breath in. It goes to the center of my breast-bone and sometimes to the back under my scapula. I have been taking very small breaths but I cannot control my yawns, coughs, and sneezes – which feels like I am getting stabbed. It seems to high to be diaphragm and too much on the side to be a “catch” or pleurisy. Any ideas? Would a sprain of muscle only hurt when you breath in?

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