Good morning Tanweer
Thanks for the query
As baby is only 6 days old, first rule out the common non pathological causes which can lead to this problem. I think this is the first baby of your sister, because new mothers always face these problems during first few days. Check whether he is vomiting
all that which he takes or only a small portion of it.
Small amount of vomiting is common in this age group after each feed as muscles which controls regurgitation of feeds are usually weak in newborn and improves with time. Burping in between and after each feed is important till you notice that baby burps. Keep him in upright position for few minutes after each feed.
Even if he continues vomiting you can give him Domstal
drops 3 drops as and when required and consult your pediatrician
is common in this age group called dehydration
fever due to inadequate feeding or environmental temp. Consult your doc to rule out any infection causing fever.
As like vomiting passage of stool 6-8 times with varying color is also normal in newborn particularly after each feed. It is due to gastrocolic reflex. Now again you have to look for oral acceptance and general condition of the baby to rule out other problems.
Better be in touch with your doc. and continue breast feeding frequently taking proper care of the baby.
I hope this answers your query well
Wish you and your family good health