Tightness in left chest through back with dull pain down left shoulder and arm off and on for 5 year.?

Rule out MI. You need to go to a physician for a chest pain workup. Rule out the most serious possibilities, like coronary artery occlusion and work your way down. Could be muscle or indigestion.
Please get evaluated. As this may represent something serious...A cardiac ct may help establish or rule out potentially significant causes.