That has happened to me, but it was before i was pregnant, you need to drink water, and some gatorade or pedialite, because you need the electrolytes...and you need potassium, so eat some banana.
Also you need to take your blood pressure, laying down, then sitting up with your feet flat on the ground, then standing up. If you get the same results or very close to it eat time, then you are ok. And you need to take these tests back to back. Also salt and sodium will higher your blood pressure. So try to remove that from your diet for now.