While it is true that Phenytoin sodium (Epsolin, Eptoin) can cause side effects, the one described by you is not one of them. It is also possible that momentary loss of memory experienced by you could be due to the disease (absence seizures) rather than drug.
Since such symptoms pose no danger, it is better to remain on Epsolin 100 mg twice daily. The subtherapeutic dose of 50 mg daily for your age, height and weight can lead to seizures.
I am unable to confirm or deny the utility of Yoga in the treatment of epilepsy.
If you have had no seizures in the last three years, one can attempt to stop medication under medical supervision.