Hullo Slog -
sounds familiar! I had experiences not unlike those you describe here. In my case it was about: hm, do people notice I drank alcohol last night and went to bed too late? And indeed: do they notice I am 'not like them' (for having OCD, that is)? In retrospect, I can laugh about that: first, I knew for sure that esp. the younger people in those places (students, mainly) probably had hit the sack at 5 AM in a state. Second: it was plain silly to think that I was the one with some disorder, and all others were showcases of bright, pure, and undiluted health and sanity. But well, the moments one suffers from it, it's far from funny.
I guess part of these feelings can be named: social anxiety disorder (SAD), which is an officially recognized form of anxiety. It can bring with it somatic (bodily) symptoms, like sweating, trembling, and sometimes dizziness.
Tips: expose yourself as much as possible, sort of a personal CBT. From experience I know that when one feels during shopping: oh, how happy and relieved I will be once I am at home, one is not really with the event (the shopping) itself, mentally. That's not good. Being out there among others can be a great pleasure.
Start by going with a (or more) friend(s), preferably people who know about your condition, and won't ever poke fun at you for that. All other forms of humour are most welcome. Company will greatly alleviate the fears.
Later on, you might go on your own, and then a cunning strategy might work: early on, ask other shoppers, or shop assistants, where you can find this or that item. Draw them in, ask which after shave would be best suitable for you, or what mixer is best suited for a single person household.
Believe me, this works to great effect. Persistence is the key. At certain points in time, you will feel confidence building up. One of the finest experiences is: to start feeling like just another completely anonymous shopper, not like someone with a special and shameful problem. A number of anxiety symptoms will just cease to be. Which is a cause for celebration.
And then, one day, you will accidentally, in a crowded shop, drop a bottle of red wine. And after a brief jolt, and some shame, you will notice that an assistant quickly will put you at ease and wipe the floor. No harm done, and trouble over.
I hope this helps, well, it worked for me.
Best to you too, mr/ms (?) Slog, from Cuthbert. Hope you had a good shopping day!