Hey Holliow,
I am wondering how much you weigh? I know that you probably don't want to write it though, could you perhaps say what weight you would like to reach?
How does this feel different to your ED? Did you go to a dangerously low weight when you had your ED?
Like I said before, you are obviously a slim person anyway, because to fit into size 6, you have to be reasonably thin!
You sound like you have a great career/hobby ahead of you! To be offered a place in Competition training, you must be good!
I'm sure there is someone you can talk to? A friend? There must be someone, you may not think they will understand, but maybe they will surprise you.
I know you don't know me from Adam, but you can always write on here and talk. I know I can't fully understand how you are feeling, because everyone feels differently, but I can try to understand.
xXx Becki.