I've Been Having Sudden Dizzying Spells That Come In Pulses.

I've been having sudden dizzying spells that come in pulses. The dizzy spells last only seconds and don't hurt. There's a slight ringing in my left ear and sometimes when I move or lay down on my back I get dizzy. All this only suddenly started this afternoon and has continued for the past 6 hours. I also have low blood pressure and am a light smoker. I hope it's nothing serious...