How long should a mother follow a strict cow milk-free diet if her breastfeeding baby gets blood in his stools due to cow milk allergy?

Hello doctor,

I have an infant who is below six months old, weighs 16.09 Ibs, and height 2'17". He is exclusively breastfeeding. Two weeks before he had his second dose of the DTaP+polio vaccine and second dose of the rotavirus vaccine. Four days after the vaccination he had blood in his stools. On the same day, I ate too many cow milk products. Our pediatrician told that it could be due to the vaccine or allergy to cow milk. So she told me not to have cow milk products for two weeks. I did not eat for a week and since there were no symptoms, I was relieved and ate ice cream and cheese. On that day again my baby had blood in his stools. Now I am on a strict cow milk-free diet. My question is, how long should I continue this diet? Our pediatrician said me to continue the diet for two weeks and then we can reevaluate. Another pediatrician whom I consulted told me that it is sure that my baby has an allergy and hence I should continue this diet for at least six months. What should I do to know that it is cow milk allergy for sure? Currently, he is taking Vitamin D drops 400 IU. Can we start iron drops now or should wait for a few weeks?