Breastfeeding Failure

Feeling like a total failure and horrible mother. Little man is 4weeks1day today, went for his 1 month check up and he has lost an ounce from his birth weight. He was 6lb11oz and at 1 month weighs 6lb10oz! 😢 I have been exclusively breastfeeding. The pediatrican told me to stop breastfeeding immediately and start 2oz every 2 hours of formula. I have to go back Wednesday to see if he has gained any weight and if he hasn't, I'm so fkn scared of what will happen next. I feel like I've neglected my baby, I feel like a horrible person. This happen to anyone else? 😭