Good day. Please advise. For three weeks now we've been on the S-feed…

Good day. Please advise. For three weeks now we've been on the S-feeding regimen, for two weeks we gave it three times a day, 60 ml at a time. We went to see the pediatrician, she said give five times 60 ml or three times 90 ml because the baby has a strong direct underweight. And so we started giving it that way. Now there are problems with stool. We wait two days and help on the third. We don't give water, breastfeed on demand. What do they do in such cases on S-feeding? I'm first dealing with S-feeding. Return to previous doses? (underweight more than 1 kilogram).