Tough pregnancy

Chelsea • 24, Engaged, baby number 2 "on the way" it's a boy. Spend my time chasing his 2 year old sister around<3
This is my second pregnancy, my first I passed out a few times just from being dehydrated but this time around I'm passing out a lot more. Anyone else? Have an inside oh what to do. Been to the doctors had CAT scans and everything else the only thing they can come up with is my blood pressure drops too much when I stand up quickly. But I have passed out while standing.