What you describe is the results of unrelieved anxiety. Body is exhausted by the 'flight' it has been through in store. Exhaustion is a common experience for all of us who suffer from severe anxiety or agoraphobia. Good for you getting to store! I believe the best way to tackle stores is a focused shop.
I do it @ grocery store. Zoom around, no browsing or standing in front of packages reading labels! Nothing wrong with this. When I am in large stores, concentrate on one area only. My doctor talked to me about this method. This week caught a sale on summer jewelry and realized I was having fun. No anxiety......until, I began wandering around the place. As soon as I felt odd, headed for door. Can always go back .....
No comment on bp issues. Anxiety can push up ...but not sure about more than that.
BTW: After fainting and vomiting in Starbucks following my son's memorial service I am totally over this fear. It wouldn't have happened if I had taken a small dose of clonazapam before service. People are kind when another is in distress: bottom line, faced that fear: have returned to same Starbucks until the anxiety has disappeared.
Take care and post when you feel like it.
I also suffer from fatigue severly from my anxiety, but find myself more exhausted by thinking of the fatigue which in the end is from my anxiety. I find if I take my meds later on in the day rather in the morning, I find it helps with the fatigue during the day, although it is a little tougher waking up in the morning. I think you need to try something that will help you control your symptoms more so you experience less of these attacks. I would run your symptoms by your doc and also get your bp checked out, just incase your experiencing these pass out like problems from bp issues. Anyways, take care