Hi, Welcome to Health care magic forum.
As you describe, it appears to be the lactose intolerance
I advise you to consult a pediatrician
for diagnosis and treatment. You may need to have the stools examined for reducing substances.
I usually prescribe to my patient with such symptoms soya milk powder,avoid mother milk, animal milk, or formula milk,if confirmed for lactose intolerance.
, colicaid drops,and lactic acid bacilli.
Wishing for a quick and complete recovery. Thank you.