Some of these reactions can be due to low thyroid (anxiety is a very common symptom) and adrenal issues (both together are very, very common). The last thing is what's referred to as orthostatic hypotension. I have that problem alot. What helps me the most is keeping hydrated and drinking water with electrolytes and even water with sea salt (which is good for the adrenals). Dehydration is the number one cause of this problem - some of us tend not to drink as much water in this cooler weather, but you really need to (I'm having a similar problem right now myself). Look up orthostatic hypotension in Wikipedia and it sounds just like what you're experiencing and notice that they mention Addison's which is an extreme case of adrenal problems. Borderline adrenal problems, which effect kidney function, which effects the ability of your body to maintain good hydration.
Both my sons have had that problem, as well, and they've just been diagnosed as hypothyroid. Low thyroid function will also impact your heart and really just about every system in your body as the enzymes necessary for all these functions are not working properly. What's happening with the hypotension is that when you stand up, the blood pools in your feet, so your body will do everything it can to keep the heart going, including shutting down blood flow to the extremeties.
The tingling etc. could also be due to low vitamin B12 or Raynaud's which is very common in this colder weather and it also goes along with thyroid problems.
Your reaction in stores may also be an allergic reaction due to all the chemicals found in new products - all the plastics emit lots of VOCs, as do any products made from pressed wood. Almost all new clothes are treated with things like formaldehyde. And, you may have chemical sensitivies (again - very, very common with low thyroid function and adrenal stress).
I used to have all these problems until I got adequate treatment for my low thyroid function and take supplements to support my adrenals.
While it can sometimes be a good idea to go to the emergency room, normal tests that they will run won't find a thing wrong - they've got to catch you while the attack is still fully active.
And, overall, only a good functional medicine doctor will be able to put all this together.
Update: I highly doubt it's MS - MS is often misdiagnosed and is frequently due to toxin exposure (which can be environmental or caused by chronic infections - any living organism in your body will produce toxins, just as humans output toxins daily in their stool). Check out:
www.biotoxins.info
And, MS can often mimic Lyme disease or a root autoimmune disorder - celiac disease. We were just discussing the correlation of CD with anxiety (and nutritional deficiencies like B12.
I will definitely pray for you, but if you do have thyroid and adrenal problems, stress is your worst enemy, so please relax and leave this in God's hands !