This happens to me every time I go shopping now! I usually have to find a sheltered place, stop and sit down until I feel better. Last time, a psychiatrist just happened to find me behind a display of honey. Tried to give me a pep talk, but it was just annoying because suddenly everyone was interested in what was going on! And I just ended up going home and getting someone else to get my groceries for me. Maybe, if you're on medication, time when you take it so the most effected time hits right when you need it the most? Or, try taking a bottle of water or something to drink with you.... idk why, but drinking water helps me a lot. It has been suggested to me that perhaps I should get an emotional support dog- maybe you should look into this too.