Go to your doctor.
I can't promise that they will help the way you need to be helped, because I'm afraid EDs are not given the time they deserve by some GPs. I went to my GP in Jan, and I had to see her three times over 6 weeks. My BMI was 17.5 the first appointment, and 17 the next. However, on my last, she didn't weigh me. If she ahd have done, I would probably have been sent straight to an inpatient unit at hospital, because I know I must have been ill at that point as my BMI had dropped to 14.9 by the next week.
However, she was lucky in that I lied to my parents about my weight, and so no one knew. As the only medical professional monitoring me, it was a gross mistake on her part not to weigh me. But I digress. What she did do, was refer me to a psychiatrist, who I started seeing in Feb., who in turn referred me on to a dietician, paediatrician, and recently a cardiologist as well.
Your GP is your first step to getting the help you need. Even if they don't behave ideally, try, try, and try again. You deserve more than your eating disorder.