I have been fainting alot lately - it is annoying, i never get to do the things i plan to do..

Fridaymorning at school, we had "English-class", suddenly it felt like all my strength vanished. my heart beated real fast,my eyes my sight got blury,and i breathed heavily.
I fainted - i was gone for 4 minutes, it`s actually quite long -ambulance,
doctor-center, they took all kinds of tests..
hospital..
checked me for everything again , couldnt find anything
wrong actually.. like always.
3hours afterwards i went to the bathroom, on my way back i fainted in the hall, and smacked to the floor, a sick man in a wheelchair called out for help and the doctors came, they carried me back to bed. took the tests all over again.
like blood-pressure,tested my blood for oxygen,tested my heart-rhythm,took a CT off my brain and x-ray off my lunges,checked my reflections and so on.
i`m glad i could go home today- my mum came (1,5hours drive) and brought me back home.
My doctor ordered me to take a break from my life,
for at least 4-5 days.