Thanks for posting your query.
With the available described symptoms, there could be possibility of acute gastroenteritis
and penicillin both may cause watery diarrhea
bu presence of abdominal pain
signifies for abdominal infection.
You should consult with internal medicine specialist/ gastroenterologist and should go for thorough check up.
You should go for complete blood count
, serum electrolytes and renal function test.
You should take complete antibiotic therapy, probiotics, antispasmodics.
You should avoid both prilosec and penicillen.
You should maintain your hydration by taking potassium rich supplements.
Avoid milk and all milk related products such as cheese and butter.
Dr. Mayank Bhargava