Is he on formula? Definitely sounds like reflux or dairy allergy Try almost sitting him up while you’re feeding him and let him sit up like 10-15 minutes after he eats before burping him Both my babies are reflux babies and this helped so much
i would consult with pediatrician but have you tried cutting out dairy from your diet ? sometimes babies who are breastfed have cow’s milk allergy. Also trying colic drops incase baby just has reflux