for a period of time, I felt 暈 and saw the things up side down. I visit doctor few times and he said I got a cold. Later on I felt 暈 again, time by time not stop, but not very serious like you.
Now, i get better and very seldom the above situation. it is rare happened in summer and very hot weather. and i alway keep my body warm. i am sure that is it the chinese called not good blood circulation.
so try to keep your body warm and avoid the cold drinks is a must.