Poor digestion in my baby. Stop motion!

Respected Doctors I am sharing my 8 month running son digestion problem. He is on breastfeeding and on cerelac banana pury dal and rice water. I started cerelac on 1st of September and my son was eating well two times a day. And he looks little healthier. After 15 days spinach soup was introduced and don't know after 15 days he started doing potty 3-4 times a day and gradually 5-6 times and till now he is doing in such number. He does semisolid stool greenish dark then watery . And also whatever he eats he pooped next within 5 minutes. Now he is reluctant to cerelac also. Only drink breastmilk and banana pury. I tried ors throughout the day zinc syrup but his condition is not corrected. Even after drinking water he pooped out. And today he pooped one time a manner like only water comes like someone throw water and then semisolid . His stomach becomes badly upset. His weight is also reduced . his body  become lose. Now what should I do now. How to correct his digestion and stop motion