A little bit of blood and chest pain a few days before menstruation is considered to be due to fluctuating hormone levels, pregnancy and other factors. 1. Fluctuating hormone levels: Generally speaking, a few days before menstruation, due to fluctuations in estrogen and progesterone levels and an increase in prostaglandins in the body, the uterine lining will gradually fall off, and a small amount of bleeding will occur, which may also stimulate breast enlargement and chest pain. 2. Pregnancy: Generally speaking, six to seven days after the formation of the fertilized egg, the fertilized egg will enter the uterus, and there may be bleeding from implantation. At the same time, the level of estrogen in the body rises, which also promotes the development of the mammary glands, resulting in chest pain. If the patient is accompanied by gastrointestinal symptoms such as nausea and vomiting, and delayed menstruation, there is a high possibility of pregnancy, and it is recommended to go to the hospital in time for examination. There may be other reasons for the occurrence of blood in the first few days of menstruation, accompanied by pain in the breasts, so it is recommended that the patient go to the hospital in time to find out the cause of the problem and treat it accordingly.