Many things could have happened, the most likely things to have happened are a seizure or a black out.
When a person has a seizure, they do not remember anything about when it happened, so this is the least likely possibility, as you would not remember the feeling dizzy, etc.
However, when a person blacks out, it is due to low blood pressure, which can cause you to get dizzy, light headed, etc.
Based on what you have told me, I would come to the conclusion that you blacked out, it is probably time for you to pay a visit to your doctor to assure it isn't something serious.