My Son Is 4 Months Old ,he Is Breastfeed Baby.from

My son is 4 months old ,he is breastfeed baby.from last 15 days he is not drinking milk properly.he plays a lot but when I take him to milk he cries alot and passing stools for every 3 days.my ped said he is gaining weight nothing wrong.he suggested neopeptine drops.bt I used bonnisan b4.among these which one is better