Constant body itching more persistent at night i have epilepsy grandmal none since first diagnosed on meds for a few years. what could it be?

Check liver function: especially if your appetite is off. This could be an adverse reaction to the medication or even a delayed drug allergy. Or it could be an issue unrelated to medication (dry skin, bed bugs, change in fabric softener or laundry detergent causing a low grade skin reaction. If the itchiness is localized to one side of the body and spreads from one area to another think partial elementary seizure.