Hi Paula,
The chewing helps me to distract the feeling of faint / collapse. I also take something to drink with me and my mobile. Perhaps you can do that. At the beginning I had problems to go out as well and I just went outside and went up and down the street. Just as long as I could see the house. I think that all the neighbours considered it to be funny but, well. Perhaps you have something like a mail box or a telephone box where you can walk, or a shopping window. It's a starter.
By the way, I really thought long about the post of Vale (you read it too) where someone described how he got over it, just by accepting that he can't "win". You know, I had given a lot of things in the past 13 years (first the eating disorder) and I just want to live again. I am thinking, please dear panik attack get as hard as possible, you can only destroy the "little voice inside" but not my body. And it works, truly it does. Okay, it's one day but well.
Wish you all the best