Hello and welcome to HCM,
The symptoms of burping, stomach pain, dry heaving, and
diarrhea are suggestive of infection- infection of the gastrointestinal tract.
Antibiotics are needed to control the infection which as you have mentioned have been started by your doctor.
Diarrhea depletes water and electrolytes from the body.
So, fluid and electrolyte also needs to be replaced.
You can start oral rehyration therapy after consulting your doctor to make for the fluid losses from the body.
As you have mentioned that any fluid intake is making your son sick.
in this case, start slowly.
If it does not work, intravenous dextrose can be given to maintain nutrition.
However, this has to be done only after consultation with your treating doctor and if it is very difficult to take anything orally.
Thanks and take care
Dr Shailja P Wahal