How rare is it for epilepsy to just pop out of the blue. no family history, never a seizure, normal eegs, no major head trauma, just come out of the blue at age 21?

Yes, it happens and negative or normal EEG does not rule out epilepsy. Please follow with a neurologist.

Not unusual to acquire epilepsy in your 20's, but do you truly possess epilepsy? Your post describes "normal EEG's", and "never a seizure"; so, this seems to negate any seizure disorder, and there is no described risk factor. If you suffered a seizure, 6 yrs ago, you might discuss with your neurologist, how you handle the future.