Such severe intensity stomach pain is not very usual in isolated stomach infection
. In stomach infection the pain is colicky in nature, it is not a constant one. Was there any such episodes of pain abdomen and vomiting in the past as well?
Oral anti-spasmodic analgesic tablets to relieve the pain as required.
Oral proton pump inhibitors like pantoprazole- domperidone
combination: once before breakfast,
to relieve heartburn and gastritis.
I would suggest oral antibiotics
only in case of stomach infection after clinical examination
In case these does not help , get a couple of investigations done :
1. Complete blood count
2. Serum amylase, serum lipase
3. Liver function test
4. Ultrasound abdomen
These investigations would help to rule out any underlying intra-abdominal pathology such as acute pancreatitis