I tend to get really panic-y too. Take a deep breath. Trust your doctor, trust the process. Give it a chance. If you start eating more, and no longer lose weight, or even gain a small amount, you can always tweak it back to eating less. You won't be doomed to never be successful again.
And also just try to focus on other things in your life other than your food and weight to try to keep from freaking out about food and weight loss so much
Much easier said than done, but it's what I'm trying and I hope you can pull yourself out of this, even though it will be hard.
Please update us, I'll be sending you non-panic-y energy!