I am an Epileptologist responding to you
Before i respond to your question, i will tell you that the treatment of epilepsy
depends upon the exact classification. This can be done by clinical evaluation, EEG test and MRI
scan and if needed genetic/other tests. All these tests will help us classify the type of epilepsy and help us select a good medicine for the patient.
Back to you, The medicine that you are taking causes weigh gain. In the absence of other data (the exact type of epilepsy, EEG can help classify the epilepsy type), though it is not wise to advise medicine, the other options could be Topiramate
(this will help you loose weight), lamotrigine
, levetiracaetam etc. Please visit a neurologist/epilepsy specialist and they will help you select a good drug which will help you in both the ways