Have you had a proper hands on examination of your upper body because if you eat well and exercise then perhaps you have an internal injury, like a torn ligament which is present all the time but is aggravated by, certain movements, certain stretches, coughing or sneezing. The pain in your chest may be referred pain from your abdomen in the case of an ventral hernia which affects mostly men starting at the age of 20 years. These are also called epigastric hernias. You get plenty of information in a search engine. They can be extremely difficult to find even by a trained GP but if they trap a nerve or blood vessel they can give extreme pain.