Welcome to HCM,
Your son is having jaundice
his age is 1 month, in this age there are few possibilities which are most common,intially enzyme glucuronosyltransferase which normally converts unconjugated bilirubin
to conjugated bilirubin that can be excreted into the gastrointestinal tract may be there.
By this age physiological jaundice should improve,
Other problem may be breast feeding jaundice and breast milk jaundice.
Usually sunlight or photo therapy is good enough.
But if your Pediatrician
has given phenobarbitone
it is known hepatic enzyme inducer so as to induce enzyme and convert unconjugated bilirubin to conjugated one and improve it fast.
Best of Luck.