Hi AnneS, welcome to CWE!
Auras can be considered "Simple Partial Seizures", especially if they aren't followed by a migraine headache. Often simple partials originate too deep in the brain to show up on EEG, so it's not unusual to make the diagnosis without test confirmation. In fact, one way a diagnosis is confirmed in the absence of a positive EEG is for the symptoms to respond to medication -- and yours do.
I understand your frustration -- unfortunately it can take a while to get the right dosage or med to control the seizures. And sometimes seizure disorders change or our metabolisms change, and the treatment has to be adjusted accordingly.
As for the "cause": The majority of seizure disorders are idiopathic -- that is, there is no known primary cause. There CAN be secondary triggers though, and if you keep a seizure diary you may be able to identify them. The #1 trigger is fatigue, but there are many, many kinds -- low blood sugar, dehydration, nutritional imbalances or sensitivities, infections, hormones, flashing/fluorescent lights... In general, it's good to look out for potential physical, physiological, and emotional stressors, and avoid them where possible.
Best,
Nakamova