Twice in the last week, when I have been outside working in the garden or cleaning out the car, I suddenly start having labored breathing and feel weak, like I need to sit down. My hands and legs feel shaky and I feel exhausted -- almost like I m having a low blood sugar attack but it seems different from that. I came in the house and thinking it might be low blood sugar, I had something to eat and then laid down. After awhile I feel better but still real tired. IS this a low blood sugar attack or could it be something else?