It is perfectly safe to use antibiotics while breastfeeding. Contact Le Leche League or a lactation consultant for more information. You do not have to stop breastfeeding!
Keep breastmilk production up by pumping breast after every bottlefeeding and toss the milk. Milk pumped from both breasts combined equal what baby drinks in the bottle each time.
Most antibiotics are safe to take while breastfeeding. Talk to your pharmacist. If its one of the few not safe to take see if there is a safer alternative.