Hello rajeshchandani , greetings from healthcaremagic.com . I have gone through your case history and I would have expected a more elaborate history from you as this is not enough to come to a meaningful conclusion . It is very unlikely that your stomach problem and indigestion can give you dehydration. How long are you having this problem of yours is it through out the year or seasonal mostly during warmer climates ? Have you noticed any change in your skin complexion and loss of weight inspite of healthy eating ? Do you suffer from frequent fever ? Do you suffer from thyroid diseases and other co morbid conditions like hypertension ? You did mention your CT scan done for your chest and abdomen is within normal limits so I rule out any structural abnormalities . I would narrow down my doubts on either your thyroid or your adrenal system but I am only interpreting it as per your case scenario , which is not substantial enough . My advice to you would be to consult with your primary physician and then with an endocrinologist. Hope I have been able to help you . Take care .