Long time, no psychotic episodes (HA-HA-HA!!!)
OK, I'm a little sarcastic today. Unfortunately, I think your doctor is ordering a bunch of scary tests that you really don't need. A state of depression or flashbacks can't be diagnosed by taking a MRI. Likewise, unless you are actually having a seizure, medical equipment(EEG) isn't going to detect anything.
As far as the flashbacks, are they about good things or bad experiences? Talking about them with a counselor/psychologist can help you voice your experiences, and sometimes just that can exercise the demons if the flashbacks are bad. Writing your feelings down in a journal can help quiet things in your mind. If the flashbacks are about good things, sharing them with someone else can greatly improve your disposition. You could also write them down in a journal, and maybe this will help you not be so distracted by them.
As far as the "seizure" symptoms, they sound exactly like a Panic or Anxiety attack. If you are continuously conscious and thinking while you are experiencing an "episode", then it's probably not a seizure. Plus, seizures usually last less than two minutes. If the symptoms last longer than two minutes, it's probably a Panic or Anxiety attack. If you are capable of trying to slow down your thoughts or control your breathing during this "episode", you are not having a seizure.
Also, many drugs prescribed for depression, panic and anxiety disorder can produce "seizure-like" symptoms. Read up on the side effects of all the medications you are taking. You will probably find what medication(s) is/are responsible for your symptoms.
Good luck to you and let us know what you find out.