For some reason if I'm outside and cold or standing up for a while I suddenly feel very sick, go white as a sheet and my head gets all prickly! My vision starts going funny and I slur my words. I have to sit down asap or I feel like I'm gonna fall down! Happened again the other day when I was chatting to my friend and could have only been outside for 10 mins. Had eaten a bit of brekkie that morning but did feel much better when I sat down, had a drink and went and got a cooked breakfast...any ideas?!