fainting

It's happened twice now. I am 24 weeks and today at work I felt so faint and dizzy I had to sit down, breathe in and out through my nose until I felt human again. It was so scary as my fingers were tingling and I really felt I could just fall on the floor. It's happened twice now and i went to the doctors today and they aren't too concerned as blood pressure fine but they are taking bloods. I just want to know if anyone else has experienced the same thing?