Chest tightness for 5 days, what are possible causes?

Heart esophagus lung. The most serious possibility is angina which is a symptom of myocardial ischemia; that is poor circulation to the heart. Another possiblity is that the tube that connects ones mouth to the stomach may have a problem. Another possibility is that the lungs are affected by an infection such as preumonia.
Serious. Need to get it check, could be lots of things including pericarditis, but need to rule out ischemia first (narrowing of artery). Go see a doctor or go to er.