I have severe anxiety all the time and take propranolol and klonopin. I also have ADHD, though I can't stand taking stimulants because they take away my appetite and keep me from sleeping as well as making my anxiety worse (which I was amazed to discover was even possible! LOL).
My brain is always going 100 miles an hour and I guess for the most part I've learned to live with it. My thoughts, however, are not always so negative as yours are. I've tried classes on meditation and yoga, but I can't keep my mind from wandering long enough so I didn't find them particularly helpful for me, though I have seen them do wonders for others. I think it's my ADHD that makes them so difficult for me.
I also have to agree with Weownthesky. Music is very helpful. There's a Native American flautist named Carlos Nakia who has the most calming affect on me, though I will listen to just about any kind of music when I need to 'turn off my brain' for a while.
Good Luck and I hope your problem gets better. I think your T is on the right track.

WW