What Causes Fainting Sensation?

I experienced a 10 sec faint wave Wednesday am after drinking 8oz coffee -new coffee pod from Java factory I did not hit floor but walked 3ft to my bedroom and sat down for 10 minutes with s sip of water and aspirin Then to st Luke Er which resulted in negative ct scan and ECG today I seen cardio dr which has me on an event monitor for one month. And referral to neurologist for further test