Hi crazychick,
Since your seizures happen at the same time every month, that's a clue that your trigger may be hormonal. The best way to identify triggers is to keep a diary where you track the seizures along with all sorts of information about your general health and lifestyle. What you're looking for are things that happen in the days or hours before your seizures that might be playing a role in lowering your seizure threshold. Here are some sample triggers:
Fatigue
Hormones (fluctuating or high estrogen levels, low progesterone levels)
Food sensitivities or allergies (Additives like aspartame or MSG. For some folks, it can be dietary things like gluten or dairy, or sugar)
Infection/Illness
Dehydration
Low blood sugar
Fluorescent or flashing lights or patterns, computer monitors
Alcohol
Physical stress
Emotional stress
Not everyone can identify triggers, and sometimes it can be a combo of things that push you over threshold. In my case, I'm fairly sure that it was a combination of fatigue, low blood sugar, emotional stress, and aspartame that triggered my initial seizures. And I may have had a lower seizure threshold to start with, due to ahead injury as a child. But for subsequent seizures it's been tough to say for sure. Sometimes triggers can change, or, if the brain gets in the habit of seizing, it can take less to provoke a seizure. If you miss a dose of medication, that can trigger a seizure too.