For the past two days, i have been feeling dizzy and weak when i stand from a sitting or lying down position. it feels like i'm faint and nauseaus?

These symptoms: can be caused by anemia, dehydration, labyrnthitis, cardiac arrhythmia, or autonomic dysfunction. As you can see, there are many causes. So you should see a doctor to get to the bottom of this.

Orthostatic hypoten.: Sounds like orthostatic hypotension: occurs in response to postural change and includes generalized weakness, dizziness/lightheadedness, visual blurring or darkening, and in severe cases fainting. May result from volume depletion (due to dehydration, diuretics, or vomiting) and certain medications. Increase fluid intake and get up from laying/sitting position slowly.