Thanks for writing your query.
It will be helpful if you mention about the consistency of his stools.
After reading your post, it seems that he is having gastritis
Prilosec contains Omeprazole
, an antacid and is good in controlling gastritis.
You can add Domperidone
10 mg along with the above medicine to cure nauseating feeling.
Blood investigations including Liver Function Test(LFT) will be helpful in planning medical treatment.
I would also suggest that also get his urine examined to rule out Urinary Tract
I hope this is helpful to you.