Thanks for posting your query.
You are most likely suffering from acute viral gastroenteritis
which is also involving respiratory tract
Presence of watery diarrhea
and weakness, fatigue and cough suggests the diagnosis.
You should consult with internal medicine specialist and should go for thorough check up.
You should take complete antibiotic course, probiotics, antispasmodics, cough suppressants.
Avoid cold drinks, milk and all milk related products, oily and sour food.
Maintain your hydration by taking plenty of potassium rich.]
Take soft diet
along with yogurt and banana.
Dr. Mayank Bhargava