Tell your doctor that you are breastfeeding. He will be able to give you medicines that won’t pass into your milk. If you have no safe alternatives but really need to take meds, you can try the old “pump and dump.” Take the medicine, but continue to pump your milk so your milk supply won’t dwindle. Just throw away this “contaminated” milk. Meanwhile, rely on previously stored milk (or temporarily switch to mixed feedings) for your baby’s meals.