Recently, I've been getting dizzy at around 8 or 9 PM, and it sometimes lasts all through the night. I even wake up dizzy. Everything starts swirling in circular motion (as though I'm on a ship). My parents think my blood pressure is low. I'm possibly dehydrated (it's Summer time, and I'm an excessive drinker but recently had finals and forgot all about myself). My diet is not balanced on daily basis, but eventually I get everything needed in. Is there anything to worry about considering this condition only starts at night? Is it safe to fall asleep while still feeling dizzy? 

Thank you in advance.