The infants stomach ache is usually as a result of a colic
which comes as a result of poor food digestion. The infants' or newborn's bowel are still very young and trying to adapt to the new environmental intake of food/breast milk/artificial milk. Not properly digesting the food can lead to abdominal colic of the newborn. How do you treat this? Provide exclusive breast feeding (without even a sip of water) or if it is not possible for breast feeding, give artificial milk rightfully indicated for age for example NAN1 or 2 or PRENAN milk formulas etc. Keep proper hygiene especially on what enters the child's mouth. If colic is present already, you can provide with medications that help regulate transit such as debridat syrup, grippe water etc. If this do not help, then it is necessary to consult a pediatrician
as soon as possible.
Hope this helps