Sakit perut

Hai mommies!! Nak tanya an Anak da 4 bulan, fully bf now. Before this campur since umur sebulan. Sbb campur formula, mil kata anak i tk cukup susu. Campur formula with susu ibu la. Now i focus menyusu df cause i duk rumah je. Why my baby after menyusu df, mesti berak. Kiranya berak dia kerap dalam sehari. It's normal ke or i should go hospital? Berak dia agak cair and like normal baby poop la.