Yes, i have a low tolerance for caffeine and it took years for me to figure out that my anxiety and stress and other health issues were triggered by caffeine. I figured this out on my own after having numerous amounts of medical tests ran on me and the doctors insisting that I have trigeminal neuralgia.. They put me on awful medication that made me sad and depressed and there was no way on Gods green earth that I was going to continue living that way.
So one day, I decided to quit the caffeine. Now i'm talking only 2 cups of tea a day and maybe a soda. Anyhow, once i quit, all those issues went away.. I still get anxiety right now because i'm in late pregnancy, but i don't take anything for it and I know its because of my crazy hormones.
As for starbucks. Those people there ALWAYS give me regular coffee, it makes me so mad, because the flavors taste so much alike that I can't tell until i'm all wired up and crazy.
Could be caffeine. Caffeine will make anxiety worse, that's for sure. If I'm not mistaken coffee's pretty acidic, too. I haven't drank it for years.
I suggest:
1. Carrying some tums or maalox to see if that works
2. Don't go to starbucks. Find a locally owned coffee house.