Thanks for providing more information.
As you describe,there may be possibility of Irritable Bowel syndrome as it's a functional disorder.
There is no specific test for IBS, although diagnostic tests may be performed to rule out other problems include stool sample testing, blood tests, and cat scan, ultrasounds, endoscopy and colonoscopy.
As your test results are negative,it may suggestive of IBS based on your symptoms
Even stress and anxiety can be contributing factor in IBS.
You can take metamucil.
Take OTC mylanta.
You should add more fibre in your diet.
Start probiotics and eat yogurt.
Avoid caffeine, alcohol,carbonated beverages, fried food.
Do meditation and deep breathing exercises to relieve stress.
Do regular exercises.
Your symptoms can be associated with medications side effects-diarrhea,gastrointestinal upset are listed side effects of Plavix and zocor.
I suggest you to consult your Gastroenterologist again for further evaluation and management.
I hope this helps.
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