A “heavy chest” probably has nothing to do with stomach pain and green stool. The sensation of a heavy chest can be due to many reasons but at your age (26) the most common reason is usually anxiety. Of course, before blaming anxiety as the cause of the condition, lung and heart disorders have to be excluded first. You can visit your primary health provider to request information about diagnostic procedures to investigate the heart and lung health.
Stomach pain and green stools could be due to some type of gastro-intestinal infection. Gastro intestinal infections usually pass spontaneously. You can drink alot of liquids and electrolytes to prevent dehydration. For the stomach pain, you may also request a prescription for a spasmolitic drug like trospium. A diet without fats and sugar is also important during times of gastro-intestinal infection.