Billirubin level rebounds again. Baby?

My new born baby is 15 days old and on 3 day his billirubin increases at 14.6 then doctor suggested to admit him atleast 48 hours ..after phototherapy his billirubin level decreases at 7.5 but on 15 th day when we visited to doctor he again told us to do test. Tsh, coomb test, thyroid, haemogram, blood group. and all test reports comes normal but billirubin level again increases at 10.6 Baby weight- 2.9kg Mother blood group-   O-ve Baby blood group -   O+ve Direct billirubin - 1.8 Total bilirubin - 10.6 He is 1 day premature Baby is active and taking formula feeding 8-9 times in 24hrs After every feeding he sleeps. Doctor told me not to breastfeeding for 36 hrs..is there any problem to my breast feed milk..now it's more than 40 hrs still I didn't feed breast milk ..I m giving him formula milk...is it ok? Or I start breast feeding? Is it normal to increases bilirubin again??? What exactly we can do to decrease billirubin level,? Is there any harm to my baby? please suggest