Are you 100% gluten free? Anxiety is significantly more common in people with gluten issues than those without. The development of an anxiety attack is actually the first sign I notice after I've accidentally eaten something with gluten in it. As far as triage goes, aside from popping some klonopins, try a dose of magnesium malate/citrate it's pretty damned relaxing for a simple mineral supplement. Additionally you could try eating some really high fat foods and aim for fat's neat abilities to produce calmness.
"You can demonstrate the purpose and limits of human digestion with a simple experiment: eat a steak with some whole corn kernels, and see what comes out the other end. It won’t be the steak."