The main reasons for breast lumps and pain during breastfeeding are as follows: 1. The patient may have mastitis, which is caused by excessive milk stagnation due to untimely discharge of breast milk during breastfeeding, or retrograde upward infection of breast ducts by bacteria from the nipple. 2. The internal infection of the mammary gland forms a lump with red, swollen, hot and painful surface, which may be accompanied by generalized fever.2. Consider that the patient may have a breast tumor, which may be accompanied by an uneven skin surface color change, presenting an orange peel.3. Consider that there are breast nodules, which are due to unstable hormone levels in the body, and elevated levels of estrogen. If you have hard and painful breasts, you should consult the breast surgery or gynecology department, do molybdenum target examination to confirm the nature of the disease, so as to choose the appropriate treatment.