Oh don't worry, you are definitely not alone in this, so many of us felt the same dizzy spells right around week 36, it is really quite common at this stage! The main thing is your blood pressure naturally drops during pregnancy, so try to sit or lie down on your left side (not flat on your back, as baby's weight can press on a big vein and make it worse), sip water slowly, and eat something small like a cracker or biscuit to stabilise your blood sugar. My neighbour mentioned that dry ginger really helped her when the dizziness came with nausea, she just nibbled a little and said it made a difference. Small, frequent meals throughout the day rather than big ones also helps keep things steady, and avoid strong smells or stuffy rooms if you can. That said, since yours has been going on for a few hours, please do check in with your gynae or doctor just to be safe, especially if you feel any abdominal pain alongside it. Take care of yourself, you are almost there!