Hello. I m sorry you re ill. The symptoms you ve described here are very worrisome. If you have blood in your stool, there are a number of possible causes, and they are all potentially dangerous: inflammatory bowel disease (e.g., ulcerative colitis), a bleeding ulcer, infectious diarrhea, gastritis (inflammation in your stomach lining), diverticulosis and even bowel cancer can trigger gastrointestinal bleeding. If you lose enough blood, you can become anemic, which could account for your dizziness, difficulty concentrating and chest pain. I suggest you seek medical attention immediately. Good luck!