What Causes Severe Pain In The Chest On The Left Side?

Sharp, stabbing pain with forced expulsion of air in upper back and chest, left side only. Complicated cold/flu for past ten days with mild fever with severe headache and fatigue accompanied by coughing spells (dry and productive). Cough persists. Typically dry at night and productive during the day (yellow and green sputum). Short, shallow, guarded breaths at night to avoid induced cough (inevitably cough). Course of amoxicillin began 72 hours ago. Chest X-ray was negative or unrevealing for pathology. However, X-ray taken 4 days ago BEFORE above symptoms manifested themselves. Swab taken for Strep. Results not yet available. Differential diagnosis for strained or torn intercostal muscle vs. pleurisy requested. What further follow up would you suggest? Up to date imaging, perhaps? Please fell free to use medical terminology if need be. I will understand. Thanks. Alek.