This Morning I Woke Up And Felt Fine. All Of

This morning I woke up and felt fine. All of a sudden when I got up from the chair I was extremely dizzy. This continued for about 2 1/2 hours and additional symptoms of nausea, sweating, paleness were also present. I was unable to stand, walk drive or even sit without the world spinning. After lying down for a couple hours, the problems went away as quickly as they started. Now all I have remaining is a dull headache. Any ideas?