Exclusive breast milk till 6 months of age is the best for your baby.
Nothing can replace breast milk.
Since you are giving breast milk too, try to augment the output of breastmilk.
Take enough rest
Eat a healthy diet that includes lot of fluids, fresh fruits, vegetables, dry fruits, nuts, milk, non veg (if you eat).
Take your calcium supplements
Sit in a calm place, relaxed and feed your baby.
The more she suckles, the more will be your breastmilk production.
If you start supplementing, your breast milk secretion will automatically come down.
Due to numerous reasons, breast milk is the best for your baby.
Among formula, nothing is superior. And the problems of colic
will be more with any formula compared to breastmilk.
Best wishes and happy parenting