Baby Allergic to Breast Milk

Had to take the little one to the pediatrician yesterday for mucus and blood in his stool that hasn’t gone away since the last time we took him (about a week ago) and now they have me switching to formula because they think he’s allergic to my breast milk. They said to try and reintroduce breast milk after two weeks if everything clears up and see what happens. With the national shortage going on this is only stressing me out and I can’t even begin to explain how disappointed I am that I can’t breastfeed him right now and possibly won’t be able to again.