I would make an appointment to see your primary care physician ASAP. It sounds like you fainted (not enough blood to the brain), so your doctor will check blood pressure, ask you what you ate and drank that day (you may be hypoglycemic) and look into diabetes and other factors.

In the meantime, it may be a good idea to sip orange juice every few hours and stay off of your feet.

I hope you feel better soon.