First let me say that I have battled with the same over restrictive/ over exercising cycle with binge eating. And truly, it always feels like I'm the only one in the world that lives with this monkey on my back.
Even when logic says "eat more", this weird gut feeling / guilt/ fear/ I don't know what it is says "NO! you'll gain weight!!" ~ This feeling can not be reasoned with. I've tried.
You're working with a therapist and that is excellent, rather than trying to defeat it alone. My only suggestion is whan the moments of not being able to eat or binging strike, write down what you are feeling. I'm not saying that will help you in teh moment. Unfortunately you may face more over restricting / binging before beginning to heal, but at least you will have an in the moment picture to bring to your therapist. Perhap that will help with working through these feelings.
I'm sorry I couldn't be of more help. I haven't figured out how to "cure" this, so I still deal with this everyday. Its like my secret cross I bare.