Left breast and back pain may be caused by labor and cold, heart disease, lung and chest disease. 1. Exhaustion and cold: the first thing to consider is exertion and cold, do not pay attention to keep warm by the cold air stimulation, and at the same time weight bearing or late-night work, sitting posture is unreasonable, there will be excessive fatigue of the back muscles, causing the left chest and back pain. 2. Heart disease: such as: angina pectoris and coronary artery blood supply insufficiency. It is usually caused by excessive emotional fluctuations and increased oxygen consumption, and usually results in chest and back pain with pressure. 3. Lung and chest diseases: such as pneumonia and pleurisy. Infectious diseases, autoimmune diseases prone to cause pleurisy and other diseases, resulting in pain and discomfort in the chest along with the back. It is also accompanied by coughing, coughing up phlegm, fever and other symptoms. There are other causes of left breast pain back pain, it is recommended to go to the hospital to avoid delaying the condition, resulting in unnecessary harm to the body.