Have you not taken any medications so far?
Did you eat out prior to that?
Is he having vomiting and fever as well ?
Hospitalization is advised if he is not taking any fluids orally and is dehydrated with drop in blood pressure.
What I suggest is go to a ER physician and get the clinical examination done for temp, pulse , blood pressure , dehydration
In case his vital parameters are fine he shall recover with oral medications like:
1. Oral antibiotics
(Because its been 6 days) . Tab Ofloxacin
course for 5 days.
2.Oral anti secretory agents (tab redotil ) short course for 3 to 4 days .
3. Oral Proton pump
inhibitors - domperidone
tablet like Pan D once daily before breakfast for about 7 days.
4. Oral rehydarting solution (ORS): Frequent sips as much as tolerated to prevent dehydration.
But at any point if he is not able to retain the oral medications and throws up , or oral medications are not helping and his dehydration and frequency of loose motion
worsens then do take to hospital immediately.
He shall need IV drips and IV antibiotics.
Also in that case investigations suggested are: 1. Complete blood count
2. Stool for culture and sensitivity.