Medication is great if someone else is doing the driving but here it amounts to a DUI and so for me it's been a matter of having to do much of what Bloom spoke of...pay attention to what, when, and why.
I go through periods of time when getting out seems to be no big deal and wham! it's a HUGE issue where I am shaking, in tears, unable to catch my breath, and quite literally unable to step out that door - a day, days, weeks, more???
Mindful activities are extremely helpful in getting back to the here and now but will not prevent or give me understanding of where these are coming from and (for me) there's a pattern to why these suddenly come up and smack me in the face.
I have found, like SimplekindofGirl, those all night stores work the best for me...less stimuli going on so I don't end up becoming overwhelmed and easily confused.
You seem to be pinpointing the source, keep going at it and posting. You are far from alone on this. Taking the fear out of the unknown goes a long way to helping resolve the problem.
Peace,
Rain