Trying to decide if I have common flu or something more. I am a smoker. A few days ago, I had a sudden onset of pain under my left rib and running up to my shoulder. It was difficult to breath other than shallow breaths. it lasted 2 to 3 days also in that time I developed a high fever with horrible body aches . Since then , while the pain in my left side has improved, I still run a low grade fever, dry cough, and body aches with some shaking..