So, Had Some Back Pain Last Week, Went To PCP,
Possibly gastroenteritis.
Detailed Answer:
Hello dear, welcome Ask a doctor's service.
I read your query and here is my advice.
I think you may be suffering from a viral gastroenteritis. I don't think it can be related to kidney stones just occasionally happened after back pain due to kidney stones.
Diarrhoea due to gastroenteritis can last from 5-7 days and since it is getting better the fourth day it is more likely to be gastroenteritis.
Eating yoghurt, toast is a good idea.
Drink water to keep yourself hydrated.
Don't drink fruit juices especially apple or orange juice or sweetened beverages.
Don't eat too much fibers.
Eat small portions often.
I don't suggest you to have intravenous infusions yet.
Hope I have answered the question.
Let me know if I can assist you further.