should i slowly start interduceing back my breastmilk with baby ?, its day 2 useing just the "…

should i slowly start interduceing back my breastmilk with baby ?, its day 2 useing just the " Nutramigen" formula on him that his doc prescribed for me to use bc i needed to see how he act with this alone, he tested positive for milk allergy 3days ago due to a poop that had a little mix of blood and im not sure if it was bc i had ben giveing him half enfamil formula mix with my BM, since he was about 2 1/2 wks old or was it bc of my BM only I have not yet done BM alone on him for a full whole day so maybe i should see n test that out,

before he was starting to get really fussy on n off nd fight his sleeps, his gas was some what painful to him agian wasnt sure if it was cause bye my BM or the enfamil im so confused bc ive so far have eliminated drinking coffee and eating pizza those are the two things I did most that had dairy in it, but my stash in freezer im sure has wat ever it was he was allergic to in it IF that the case with my BM... im just confused on wat to do i wanna kp nurseing him lactation consultant said he's not allergic to my breast milk i still can give it to him but i need to finde out what certain food or what i drank that I had in my blood that, he seem to not do good with "again if that's the case with just my breastmilk".....