What Causes Cold Sweats And Convulsion For A 19-year-old?

I m a 19 year old female at 5ft 6 and 10 1/2 stone. I just had a blood test today and was nervous as I have had adverse reactions in the past such as passing out whilst sitting down followed by a seizure. I went to have a full blood test earlier today, however I laid down to prevent a repeat of the previous time. I managed to keep consciousness despite my head spinning, however it took me 5-10 minutes to gather the strength to stand p. I then took a seat in the waiting room to compose myself before leaving but my hearing then suddenly went, I broke into a cold sweat, couldn t speak without slurring. A doctor was called and I was laid down and then started to convulse as if having a mini fit. The doctor checked me over and once he was happy for me to leave I did. I m wondering if this is normal, as my body clearly isn t good at taking the experience of blood being taken or whether this is something more worrying? I still feel very weak now and wobbly as if drained of all energy.