Thanks for providing more information.
As you describe,your symptoms are suggestive of Postcholecystectomy syndrome( the presence of abdominal symptoms after surgical removal of the gallbladder) in which increased bile flow resulting in indigestion, bloating,diarrhea.
It is advised to take fat -free diet.
You should avoid caffeine, peppermint, chocolate, smoking.
You should eat fruits, veggies,wheat bran and whole grain(unrefined) products.
You should increase Vegetable Protein (especially soyaprotein ),foods containing Pectin (Apples) and foods containing Cellulose (Celery and Crisp Fruits & Vegetables).
You should avoid saturated fat intake, animal meat, all white flour products and artificial food additives.
Other possible cause may include 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.
Do meditation and deep breathing exercises to relieve stress.
Do regular exercises.
I suggest you to consult your Gastroenterologist again for further evaluation and management.
I hope I've provided the information you were seeking. If you are happy with my service, please provide a high rating. If not, please let me know so l can continue to help you. Thank you.