This is a tricky question mostly because you have a complex medical issue going on which probably needs a medical visit to get a really great answer since it would require Dr. Carney to ask you a bunch of questions. But, we can certainly look at her advice to people with the opposite problem (they are wanting to lose weight) to see what you might choose to do differently in order to slow down and hopefully reverse your own weight loss.
I just loaded some .PDF files that you could download to look at that display calorie concentration (aka density) in which we show which foods lean toward weight loss and which ones towards weight gain. I uploaded them to https://www.drcarney.com/community/groups/5-weight-control-support/33-files
The LongList is probably the best one for you to download to see what types of foods would put you into the weight gain zone. But, we would NOT recommend the last few items on the list because they are also inflammatory.
I hope that the PDF will be helpful. It will show that beans, grains, pasta, root vegetables will probably be good choices for you. :-)