Antibiotics while breastfeeding

Sally

My one month old baby is SO gassy and so sad, just screams when she is awake, nearly impossible to sooth. Been this way since I have been on antibiotics for mastitis. My obgyn and her pediatrician both say antibiotics are safe when breastfeeding but this poor baby seems to think otherwise. It looks like I may need several rounds of it too. Recommendations? Experiences? I really don’t want to stop breastfeeding