What Are The Causes Of Dizziness?

I have occasional times when I am very dizzy to the point that I have to lay down or I feel like I will fall down.. A couple years ago I was sitting down and felt soooo dizzy. I told my girlfriend sitting nexto me that I was so dizzy and at the same time it was coming out of my mouth I passed out and my skin was so clammy,. She said I was out a few seconds. Not a minute but close. She put a cold rag at the back of my neck and soon I felt better. A week or so later it happened again and I knew the signs already from the previous occurance so I immediately laid down. What could be the cause? I have had the dizzy spells again since and recently but nothing like the first one. I am on disability and have no insurance to go to doc. Can you help me? I don t have diabetes