G.B.
How sad. The breast milk has all the nutrition he needs, the food does not. I would cut the food out until he gets hungry and decides to take the milk. Food at this stage is a suppliment to the breast milk, not the other way around.
But talking to the doc would clear any worry up. They might say just stop the nursing all together, I would not do that but if the doc approves then maybe....
I would stop almost all the food and offer the bottle each and every time the baby is hungry.
The doc should also check for ear infections, throat issues, teething, etc...the action of sucking may be causing the baby pain.