Thank you for your thoughts @ragged, though I think my situation is quite different to what you describe.
I am not meant to be exercising as much as I do as I am not fuelling my body well. However, running ticks ALL the boxes for me physically and (mainly) mentally. It has been discussed a lot with my MH people and they accept (even if they don't agree or support) that I've made an informed decision. My work is very informal (scientific academia) so it's fine for me to opt out of evenings out or to 'insist' that I want to do some exercise before we go out for the evening.
I don't want to draw attention to myself though. It's a battle - try and do the 'right' and 'normal' thing or stick to my safe (but unhealthy) behaviours and know I've 'failed' in even attempting to cope with the discomfort that would come from it. For sure, I've HAD to be somewhat flexible and I've seen that the world hasn't imploded.
I know exactly how my ED developed and that I use it as a way to control an aspect of my life when I can't control other things/thoughts. I am getting help. It's very hard when I'm away though -partly because there is a large gap in my therapy sessions and that I can only email my carers.
I know that dropping the weight will make me feel a sense of achievement and contentment, but I also know that these are incorrect.
Today was mostly OK actually. I worked very hard all day, then swam then went out to eat with my boss. I am very good at hiding my discomfort and he's a really nice guy and although I think he may have considered I have some worries, he would never say anything unless I became upset or something.
Writing it all out here has helped actually.
I know recovery from an ED can take a very long time. I'll get there.