Continue breastfeeding, unless it is just too painful to do so. If you cannot continue breastfeeding, express your milk as best you can in the meantime, and restart breastfeeding as soon as you can. Continuing breastfeeding helps mastitis to resolve more rapidly. There is no danger to the baby. Rest helps fight off infection.
Fever helps fight off infection.
Treat fever if you feel bad, not just because you have it. Take acetaminophen, ibuprofen or other medication for pain as you need it. You will feel better and there is no danger to the baby, who gets only a tiny amount. Amoxycillin, plain penicillin and other antibiotics are often ineffective for mastitis. If you need an antibiotic, you need one which is effective against Staphylococcus aureus.