I can relate. My first panic / anxiety attack happened about 15 years ago and it lasted for maybe a few months until, under the advice of an internist, I took B-1 and calcium (low-medium dosage). That corabo provided the breakthrough I needed. Recently, I weaned off an SSRI and began to feel anxious (along with impatience, stiff chest, "panicky" feelings). I didn't want to take Klonopin like a shrink prescribed (it's an opiate & may be addictive) so I, again, went back to taking a B Complex vitamin, extra B1 and calcium. Seems to be helping. Did this for several days (about a week, I guess) along with breathing exercises and have been feeling a lot less anxious and panicky.
I've been also thinking of trying Kava Kava or Valerian as well but since I'm feeling OK... but I have them just in case ;- )