Perianal rash# Frequent watery stools.

My daughter is 1 month old.Since she was 5 days old she is having upto 8-13 watery stools in a day which are frothy and she developed mild perianal rash which is being treated with Siloderm ointment.But within 8-9 days when rash was noticed, rash got severe  from mild .Then Dr. advised to stop breastfeed, as he suspected rash due to acidic stools, and start Zerolac for 6 days, due to  which stool started forming,no froth, and stool count was reduced to 1.And her rash also got better and skin started healing. Dr. advised to start breastfeed exclusively again.And on starting breastfeed her stool pattern went to watery and frothy again with daily stool count of 6+ and perianal rash again appeared.As previously rash got severe skin on butts are still in healing stage. Stool test was done and reaction parameter was found to be 6 and stool reducing substance was absent. I don't understand if she is not able to digest breastmilk or she is having allergic reaction to breastmilk contents.