it is common to have decrease in stool frequency or constipation after switching from breast milk (breastfeeding) to formula feed. as long as your child is feeding well passing gas from below has no vomiting and has a soft belly there is nothing to worry about. it is normal to pass stool once every 2-3 days. also you may note change in stool color (green) after switching to formula feed. in this scenario you can try using a cotton q-tip (cotton swab). apply some lubrication on it and stimulate the rectal area to see if your child passes stool. if this does not help then try seeing your local pediatrician who can help with rectal stimulation and passage of his stool. for further queries consult a paediatrician online --> <link>
my 4 month baby has not passed stools. please help.