Suggest Treatment For Frequent Loose Motion In A Child

My son is 1 1/2 years old. He passes stools about 10 -12 times per day in very small quantities. It is not watery but semi solid. His weight has been stagnant at 9 kgs since he was 1 year old. his birth weight was 2.5 kgs. otherwise he s active with average height. He seems to be having just enough quantity of rice, vegetables, pomegranate, banana, orange etc. with some distractions. What do we need to do to make him pass stools normally ?