Sorry to hear you're going through food allergies as well. I also have the same issue with losing weight when I was already underweight. My doctor told me to eat more of what is allowed, but I agree it is a challenge. She also told me to not go the route of testing every possible allergy because most of the times these tests are not relevant. She suggested the elimination diet and then adding back gradually one food at a time to see which one causes trouble. I'm still on the elimination phase.

And yes, most of these healthy foods are way more expensive than the usual ones. I find it frustrating that gluten free stuff costs so much more than the regular. What I do is to make a lot of research and go shop where I find the best prices, either off line or online. And I try to buy in bulk or bigger packaging when possible as these have the best prices.

Wishing you to get better soon and to have enough money for your needs.