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Stool floats if the stool is loaded with fat contents. Fat and oil, as they are not soluble in water floats in water. This means what you have is probably indigestion
alone and not any active infection.
What you would need is not stool test
for infection, but a detailed abdominal examination, complete liver
function test, upper and lower GI endoscopies and other relevant test. The test can be streamlined by a competent gastroenterologist.
Your symptoms do not appear concerning and you can plan a visit to your gastroenterologist wheneever possible.
Hope this helps.