Greenish stools. Feeding for 3 days?

Hi, My baby is 5.5 months old. Exclusive breastfeeding baby and he is 6.9kg. Birth weight is 3.2. For the past 20 days he has been passing greenish stools immediately after every feeding. It's like watery consistency. For the last 4 days giving probiotic twice a day & zinc drops once a day. And last week the antibiotic was started for 5 days twice a day.( Completed zinc , probiotic & antibiotic ). And we gave a stool routine and culture test. The report was normal. Reducing substances absent and puss cells is 2-3. But the baby is still passing greenish stools but only thing is the number of times has been reduced So the pediatrician suggested to give isomil for the baby for 3 to 4 days. Can I do combination feeding for 3 days ? Like 1 time breast feeding and other time formula feed. Kindly let me know. Thanks in advance