Try not to be too terrified. If anything, at least take heart in knowing what you're up against. I definitely would agree with your therapist though-- if you have BDD, losing weight won't change it. I'm currently about 60 pounds heavier than when my BDD was at its WORST. It will morph and change to fit itself into whatever shell you give it, and the only thing that can help, is to actually treat the BDD specifically, not the issue you think it pertains to. When I was underweight, I was obsessed with how horrible I believed my hair was. Gained some weight and shifted to hating my body. Lost some weight and shifted to hating my chin. Gained some weight and became obsessed with my abdomen. Only now that I have had extensive therapy do I feel able to step back and understand that none of these things are "freakish" the way I believed them to be. It takes a lot of work, but all those times I thought losing weight was the answer, I was completely wrong.

You're already one step ahead of the game though since you are already seeing a therapist. That's great! I can only urge you to continue with that, and read up on it as much as you can. Come talk any time! How do you feel about the diagnosis? Are you terrified by being diagnosed with a disorder full-stop, or specifically because it's a BDD dx?

It does make sense, I understand. Take some time to just come to terms with it and be easy on yourself for a few days. Then, I'd recommend diving right in and researching it as much as you can so you'll be able to fight it.