I don't know the answer to your question about you in specific, but I have a genetic disorder that predisposes people to being super thin. One element of it is that fats are misprocessed.

I have made some headway on dealing with it. But, I mean, I wouldn't know where to begin to explain it and I have no idea how it relates to your experience. So, I mean, I don't know what pieces to even talk about. If I know someone has, for example, diabetes, I can come up with pertinent things to say, even though that isn't my condition.

There is a lot of info out there these days. You may be able to eventually hack this and find a means to put on weight.