I Have Been Having A Really Tight And Painful Muscle

I have been having a really tight and painful muscle on the upper right side of my back close to the shoulder area for 2 years now the muscule is so knotted up its the size of a small lemon and just recently I have lost all sensation on the outside of that area I'm only 24 and really concerned. I can't see a doctor because of no insurance.what could be causing this