Couple days ago I started having pain in my upper back left side. It gets worse when I breathe in all the way and when I cough its unbearable?

Pleurisy. The pain still has to be evaluated properly before you can say it is all pleurisy or muscle strain. You have to see your doctor for proper evaluation and perhaps with a cxr to make sure there are no other causes. In the meantime a NSAID like Ibuprofen may help.