Having a headache at the back of your head for three months is something to take seriously and should be evaluated by a neurologist to determine the cause and appropriate treatment. Persistent headaches in that area can be due to various reasons such as tension-type headaches, cervicogenic headaches (originating from the neck), or other neurological conditions.

• Since the headache has lasted for several months, it is important to get a thorough clinical assessment including history, physical examination, and possibly imaging studies.
• Avoid self-medicating without guidance, especially with medications like Migranex (Flunarizine), which is used for migraine prevention but requires a doctor's prescription and monitoring.
• Keep a headache diary noting frequency, intensity, triggers, and any associated symptoms like vision changes or dizziness to help your doctor with diagnosis.
• If you experience new symptoms such as weakness, vision loss, confusion, or severe worsening of headache, seek emergency care immediately.

Please consult a neurologist promptly to get a proper diagnosis and tailored treatment plan. If you want, I can explain more about possible headache types or treatment options.To narrow down potential causes, we will need some more information.I understand you've been experiencing a headache at the back of your head for three months. To better understand your situation, could you please share your age and gender?