Hello DeftRabbit: Well... from my perspective... you, or someone, is paying your therapist to help you. He can only do that if you are honest with him. Keeping something like this from him is really defeating the whole purpose of going to therapy. Why bother? But, in addition, anorexia can become a serious, even life-threatening, condition. It's important to explore what is going on with you in that regard before the condition becomes even more ingrained & serious than it is now... in my opinion.
I see this is your first post here on PC. So... welcome to PsychCentral… from the Skeezyks!

I hope you find the time you spend here to be of benefit.
PsychCentral is a great place to get information as well as support for mental health issues. There are many knowledgeable & caring members here. The more you post, & reply to other members’ posts, the more a part of the community you will become.

Plus there are social groups you can join & chat rooms where you’ll be able to connect with other PC members in real time (once your first 5 posts have been reviewed & approved.) Lots of great stuff! So please keep posting!