Baby allergic to my breast milk

Hello , sadly today I took my son to the pediatrician and they said he’s allergic to my breast milk and said to stop breast feeding him immediately and to give him Alimentum. I’m pretty bummed out and I honestly didn’t get the chance to ask any questions as I was getting emotional and couldn’t think on the spot. If y’all can please help me and give me some tips from your experience, thank you so much!

Does this mean I don’t pump anymore? My breast have been leaking since I left his appointment and don’t know if I should save the milk or just try and stop.

Is he allergic to specifically me or is it something I ate that he reacted to? I didn’t quite understand as I’ve been breastfeeding him since he was born. 🥺

Does formula give him a different diaper outtake? He hasn’t went #2 since I started him on formula around 3pm today, it’s now midnight where I live. I’ve been giving him 3 oz whenever he gets hungry so far he’s only had 2 bottles since after his appointment. Is that normal? Or should I be feeding him more often? (Usually when I breastfed, I fed him whenever he wanted and whenever I did pump a bottle I’d give him 3oz and he would be satisfied.)

Sorry for the MANY questions 😵‍💫

I’m a ftm and this is all new!! I’d rather hear some real experiences than looking on google all night. Thank you again .