You started too late. You should have given a bottle from day 1, when baby’s sucking reflux is strong.
@Incognito oh thanks for this very useful advice
@Elle (i can't see waves) medela slow flow and lansinoh slow flow nipple :/
Just offer a straw cup instead. :) I did this from 6mths for water and bm when it was required.
What bottled have you tried? It could be the teat 🤔