Zen Retard is the brand name. The name of the medicine is carbamazepine. If there is no attack of seizures for three years, then usually the medicine has to be stopped. You have already taken it for 8 years. I presume there was no attack; hence your doctor has quite correctly stopped the medication. Zen Retard has too many side effects. Taking a medicine without any good reason creates more problems.
Your headache is not connected with stopping Zen Retard.