There are many reasons why the breast suddenly does not rise and becomes soft, as follows: 1, milk drainage, before feeding milk gathered in the breast, there will be breast swelling and pain, the breast is harder, serious will also appear mastitis. So after breastfeeding, the milk will be drained, there will be no milk rise and the breast will become soft. 2. Pus discharge, if the pus is generated in the breast due to prolonged milk stagnation, the pus will gather in the breast and there will be a feeling of breast swelling and hardness. After the pus is removed by puncture or incision, the breast will not feel swollen and the breast will become soft. 3. Insufficient milk, due to poor nutrition or mental stress leading to insufficient milk, you can eat more high-protein foods, such as fish, meat, eggs and milk. Also relax your mood, consult a psychiatrist if you have depressive tendencies, as well as appropriate activities to ensure immunity.