How do I know if I have mastitis?

Pain, hot, red, ill. The most common symptoms include pain or tenderness of the breast, redness of the skin- often in a wedge shaped pattern, warm feeling when touched, general feelings of illness and a fever. It typically happens in the first few weeks of nursing and is generally only on one side. See your doctor to confirm the diagnosis and get treatment.
Sore lump. You will notice a red, warm, tender lump in the breast, and you may have fever and feel bad in general. This is not a reason to stop nursing, but you should contact your doctor to report the situation.