I wouldn't call 15 lbs extreme weight loss. Are you eating the same as you did before the anxiety? I noticed that when I was first diagnosed that I had no appetite, or that I would just pick at my food. And, I dropped 15 lbs in like 2 months. However, after starting meds, I have regained a normal healthly appetite, and (unforetunately) am starting to put some of the weight back on. Maybe you are just too anxious. If this is so, you may want to ask your doc about a med like Lexapro or Zoloft.
Good Luck!