This reminds of this girl's story: http://stophatingyourbody.tumblr.com/post/2568132832/hi-im-casey-im-19-52-and-feel-like-ive
I agree, ask the doctor about Celiac Disease! I also agree that lots of protein, natural fats, and complex carbs are all useful for weight gain.
You could try omelets pumped up with:
- cheeses (cheddar, feta, mozzarella, parmesan)
- calorie-dense vegetables (potatoes, legumes, yams)
- meats (sausage, ground chicken/turkey, tuna, bacon)
- spices (garlic powder, cumin, black pepper, cayenne pepper, iodized salt, etc.)
Serve it on whole wheat toast with a glass of whole milk or a bottle of Ensure.
I also recommend greek yogurt or full-fat cottage cheese with:
- dried fruits
- powdered spices (cinnamon, nutmeg, ginger)
- sweeteners (brown sugar, honey, molasses, etc.)
- and/or protein powder
I hope you find a solution soon!