My Son Has Been Taking Onfi Since The Beginning Of

My son has been taking Onfi since the beginning of August. Initially it worked beautifully in stopping his seizures. We reduced it by 10mg to 20 in the am and 10 in the pm. He started having seizures again and we re -added 5mg at noon. He was misinterpreting what was being said to him and he could not stop talking. he is currently also taking phenobarb, felbatol and vimpat. He uses a prn lorazepam and diastat. He is stil having seizures and now they are clustering at times. Should we take him off of it?