Thanks for providing more information.
Well as you describe possible causes may include Gastroesophageal reflux disease,Irritable Bowel disease,Colitis.
So you should try OTC Prilosec before meals and Zantac150 mg twice a day( morning and at bedtime).
Also hydrate yourself with plenty of fluids.
Avoid smoking,caffeine,spicy,fried, greasy food,carbonated beverages,Alcohol.
Take Metamucil and OTC Mylanta.
Do deep breathing exercises and regular exercises.
As you have history of thyroid dysfunction so this can be a contributing factor in gastrointestinal upset.
Avoid late night working and eating meals.
Further upper GI scopy should be advised and a clinical examination by a Gastroenterologist should be considered for prescribed medications even for IBS.
I hope this helps.
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