I don't know much about PDD or catamenial epilepsy, but I have been on prozac for four years. (two years before the epilepsy).
I've never heard of it preventing seizures, the worry always seems to be lowering the seizure threshold (though i was never taken off it as I'd been fine for two years before i started having regular seizures).
I have heard of it helping other meds to work better (or more strongly) though, i guess that can be dangerous, or really useful!
I have no idea what the case is in your situation, i guess you need to keep track of it and see how it goes!
How are you doing now?