If you are falling and losing consciousness this can be serious - you can get hurt from falling.
You need to be certain that you do have low blood pressure and maybe even low blood volume, and are not pre-diabetes or having thyroid problems.
The generally suggested therapy doctors first suggest to help this is to increase fluids - water and electrolyte enhanced drinks and to increase salt intake. For many this is enough to help, but you need to be sure this is ok with your doctor first.
Other suggestions are to be very careful when you stand or sit up, do it slowly. If you start to feel yourself getting dizzy sit down, no matter where you're at.
I've had this problem for years, suspected it was just orthostatic hypotenstion. It worsened, I tried to get my GP to listen but when low blood pressure was the only thing he could find he was lost. It progressed to the point that I cannot stand for more than 15 minutes or else I feel very ill, I was stumbling from dizziness (embarrassing while in public), and falling more. Finally pushing my doctor again I was given an EKG stress test -failed it, and was able to see a cardiologist who recognized my symptoms.
I was diagnosed with neurocardiogenic syncope after failing a tilt table test and am now on midodrine to help with blood pooling in my legs and to raise my blood pressure some. So there are some medications to help, should you need them.
Go to your regular doctor, make sure you glucose and thyroid levels are ok, check blood pressure, and discuss options. Good luck.
- Just to add, I myself am only 24. It seems to be young woman (but not always!) that are often affected. Were you sick recently? more stress lately?