Hi Rebecca,
I've had epilepsy (seizure disorder) for 31 years.
I'm not a professional in this field but I'm speaking from experience and pieces of info. I've gathered along the way.
1) - After a stressful period (Christmas, Boxing day etc) your natural defenses are now "restimg" so the seizure activity can get through and cause an aura or seizure.
It could also be from low blood sugar.
2) - a simple MRI or EEG my show negative seizure activity (very common) because the seizure activity is "located" deep in the brain cortex and therefore it isn't strong enough to show on the test.
I've heard from lots of ppl on 4 different epilepsy forums with the same concern.
3) - 24 hour sleep study is a good idea, ie: if you sleep on your back, your airway could be partially restricted (snoring, weight gain) and causing lack of oxygen to the brain. This may be a form of "Sleep Apnea".
(you may be able to tell if you have sleep apnea, when you wake up in the morning, you feel lethargic, miserable, tire, lack of energy, sore throat, headache)
4) - Re: side effects from Depakote, Since I'm on another med, I can't comment on that but I have heard that it causes short term memory loss.
Randy