With CT scan being normal your symptoms are likely due to;
1) Irritable bowel syndrome (IBS); this is a functional disease of large intestine which does not have anatomical pathologies.
2) Poor functioning or non functioning gall bladder; this will need an ultrasound (if not yet done) and an HIDA scan (this is a nuclear scan) to confirm the diagnosis.
Following measures would be helpful;
2) This may help;
a) Bismuth subsalicylate
b) Activated charcoal
c) Simethicone; (Maalox, Mylanta); Simethicone causes gas bubbles to break up.
d) Beano; contains an enzyme (alpha-galactosidase), which helps to breakdown certain complex carbohydrates.
All are available without prescription.
Avoid foods that appear to aggravate symptoms. These may include milk and dairy products, certain fruits or vegetables, whole grains, artificial sweeteners etc. But this is based on the personal observation for the aggravating food.
Discontinue the following if you do them;
1) gum chewing,
3) drinking carbonated beverages, and
4) gulping food and liquids.
A trial to the IBS treatment should be given to see the therapeutic response, as follows;
1) Dietary modification; you would be the best judge to choose the best suitable diet for you.
2) Antispasmodics agents (hyoscine, cimetropium, pinaverium, and peppermint oil)
This should hopefully abate your symptoms.
Please feel free for your follow up questions.
I would be happy to assist your further, if you need any more information.