I think getting medical advice - and 2nd and 3rd opinions even - is a good place to start.

With your daughter, was it actually the breastmilk that was the problem? or proteins passing through from your diet that she has issues with?

At least this time you're ahead of the game Breastfeeding is important to you, and that's really only natural. I hope you can get help to keep feeding as you'd like to

ETA - there is an LC in Perth who also does phone counselling I think who is a specialist in feeding with allergies etc