I'm glad to hear that you made an apt to see a psychiatrist on your own, Tracy. Your own doctor will be able to advise you on treatments that may be able to help you manage the anxiety attacks.
The psychiatrist that the SSA sends you to will not treat you, his job is to tell the SSA if he thinks you are totally disabled by your anxiety or if it contributes significantly to your total disability.
Several of us here have a mental health issue that contributes to our being totally disabled or that results from our emotional reactions to be totally disabled. Some of our regular posters have been approved for primarily mental health issues. I hope that you will hear from more folks who were sent to an SSA psychiatrist so that they can tell you about their experiences to (hopefully !) help decrease your anxiety about it.
I didn't see any of the SSA docs, so I can't comment on that.
You certainly have a lot on your plate right now, that's bound to aggravate an anxiety issue. I hope that with treatment for the anxiety attacks, thyroid cancer, and MS that you will get to a state that you can manage. The (limited) financial security that comes with SSDI approval could also help ease that anxiety a bit.
We'll hold your hand through the process if you need us to
Best wishes getting through all of this.