I find it so brave of you to come public with this secret. I am certain that you are not alone. I do not have any advice but I am a binger (but I do not purge - although I have serioulsy considered crossing that line in the past). I am hoping that I have resolved my problem but only time will tell.
From what I understand, I think it might be about control. You have been in control through IP but as you phase off, you may feel that you are loosing some of that control over your body, which you need so badly. I think you can be in control and that is what phases III and IV are all about but they aren't as "black & white" as the former phases and that can be scary.
I hope you find the advice and help that you seek. The only thing I can think of is some counseling/coaching if you have that available to you.
In the meanwhile, I am sending you a