How often are you having bowel movements?
Do you drink a lot of carbonated beverages?
Have you had your thyroid levels checked?
Are your menstrual cycles regular, could you be pregnant?
It may be useful to have your thyroid tested again as this can change over time.
Another possibility is a gluten (protein in wheat, rye and barley) intolerance, which can cause blotation, gas, diarrhea and sometimes weight gain. If this was the cause of your symptoms they could be alleviated by removing gluten from your diet. Your doctor may want to test you for celiac disease although people with celiac disease are more likely to have weight loss rather than gain.
Foods to be avoided for gluten intolerance include:
You can read more about gluten intolerance/celiac disease here:
It could be helpful to get an upper GI series (xray test that looks at esophagus, stomach and first part of small intestine) and /or endoscopic ultrasound (although picture quality on these can be limited.) These tests could also be helpful to rule out stomach cancer (although weight loss not weight gain usually occurs with stomach cancer).
Read more here: