I was recently diagnosed with hypothyroidism but am underweight. i experience gas, diarrhea and bloating often after eating. could it be celiac?

Possible: 2% to 5% incidence of celiac disease in autoimmune thyroid disorders such as hashimoto's thyroiditis which can result in hypothyroidism. .Crohns disease, inflammatory bowel disease, also associated with hypothyroidism.Should see physician for further evaluation for bowel disease.

Possible: There are other reasons for your symptoms including lactose intolerance. Certainly one would consider gluten- intolerance as well. Check with your doctor.