Did you get the bilirubin levels checked ?
If the unconjugated bilirubin levels(indirect) are raised then at this age breast milk jaundice is very common.
Which can be managed by stopping the breast feed and observing the levels. Bilirubin falls within 48 hours in this case.
If the conjugated bilirubin (direct) is raised then further investigations are needed to be done to rule out any underlying pathology. Levels of indirect bilirubin when above 18 can cause it to cross brain barrier which is an emergency. Conjugated bilirubin however most likely indicates an underlying liver abnormality.