Few things,

1. If milk is from mother’s one, make sure mother eats non gassy foods. Even some vegetables are gassy.
2. Change the formula if that’s not suitable for your kid. Check the stool color and change the formula to lesser strength. For examples some kids Enfalac is higher strength so much heat it produces may lead to stomach upsets
3. Change the bottle to Tommy Tippee or Dr. Brown. Both the bottles are less airy than other bottles.
4. Try not to use the pacifiers.