Hello, all right I understand you're scared so I'm going to try and be helpful, first of all an eeg will only catch seizure activity if you're having one. Sometimes you may needd to make it a weekend event to stay in the hospital so they can monitor you. Also the other tests are void most times with seizures. You should contact a neurologist because the medicine will not work unless they know the type of seziures you are having. They may do a chromosomal test. Seizures are usually triggered by something which it seems you've already pinpointed in relation to your period. Perhaps you're low in a certain mineral, you should avoid phenbarbital as a medicine and ask about Trileptal.
Definately see a good neurologist and make sure you are comfortable with your gyno also. They should work together to see what is going on. My guess is that somehow the seizure is hormonal related. good luck