Well you are not clear about the dose, perhaps it can be incremented. If the dose is already high enough adding another drug could be considered. That being said if you have been seizure free for a long time (you don't specify how long) on your current regimen, perhaps before taking other drugs with potential side effects you should weigh the benefits. It's not guaranteed that any change in therapy will make the seizures disappear forever, and if the seizures are very rare some patients prefer to take as few drugs as possible. It's not just a medical decision you should consider the frequency of the seizures, how much they affect your daily life towards the side effects and inconvenience of many medications.