Can’t gain weight no matter what

Can anyone please help me, none of my doctors have been able to help me/take me seriously. I been living with a Traumatic brain injury for 7 years now and I can’t gain weight. I can’t stand looking at myself in the mirror anymore, I’m horrified at how thin I got despite everything I tried. Now everyone keeps commenting on it. I’m so weak, my body is in pain, My posture is so messed up bc I can’t hold myself up.

The last 2 times I been able to keep my weight up was in high school when I played sports and I flux from 10-15 pounds during the off seasons fast (possibly mostly muscles but I never looked like this) and a year ago when I took a two week vacation and hiked everyday and gained almost 5 pounds (muscle weight).

Please anyone who can help me and don’t say “eat cake or junk food”.

I just want to be able to look normal and feel better and somewhat beautiful again.