What Is The Cause Of Passing Small Quantity Of Stool?

Hi, My son was born on 20th January 2014. He was born 1 month premature and his birth weight was 2.385 kg. His current weight after 6 weeks is 3.15 kg. Since last two weeks he has been suffering from one problem. He keep son passing very small quantity of stool around 10 times a day. Other than this he passes proper quantity of stool atleast 2 to 3 times a day with loud explosion. My family paedeatrician suggested stool test and no infection was found in the test. Doctor first suggest Rinifol z for one week and then changed to Vibact for one more week along with Cyclopam drops for both the weeks. Even after two weeks the problem was still there. Then he found a red zone in his anus and then he prescribed Zifi 50 antibiotic two times a day and apply protectoderm cream in the anus area 7 times a day. But still my son keeps on squirting small quantity of stool atleast 5 to 8 times a day. Kindly revert on the same.