Thank you for your help and support.
I think my main problem now is : how can I chose not to act on my urges when I know that not acting on them could cause weight gain... It's really complicated.
But in another hand, I want to stop this behaviour, more than anything else. And to stop it I have to practice "acceptance" : it's not in my power to decide my weight, but in my body's. It has a set-point, and struggling against it is a lost battle.
I have to act like an adult now. I can't control my weight, and if I want to quit for good I have to forget keeping a low weight...