Lately I have had several instances of feeling lightheaded -- almost the same feeling as when a painkiller hits your system. I have the sensation that my computer will shut down, but I m alert and fully conscious. It isn t unpleasant except for the panic that goes with it. I had a complete blood workup and urinalysis, and everything was normal. At the same time, I have neck pain, and pain in my left shoulder. Also been having auras and mild headache. What can this be?