are you eating and drinking? Lack of either of these can cause this. Do you have ringing in your ears? An ear infection or an inear infection cancause loss of balance? Maybe you should go get checked by a doctor.

this happens to me alot
it happened really bad a few years ago
i got up from my bed and i was even takeing it slow
when i stood up i blacked out a few seconds later and bumped into my dresser and a set of shelves fell on top of me
i woke up a few seconda later to my mom screaming because i was bleeding from my head

my suggestion, go to a doctor
the reson for this happening to me is still unkknown. they did ct scans and everything but couldnt find anything? good luck and let me knkow how your feeling