Severe one-sided pain behind the eye with a throbbing feeling that comes back after the painkillers wear off is most commonly due to conditions like cluster headache or migraine, though sinus infection or nerve-related pain can also cause similar symptoms. Because the pain is recurring and intense, simple medicines like ibuprofen or paracetamol may give only temporary relief and are usually not enough. For proper treatment, a doctor may prescribe specific medicines such as Sumatriptan for quick relief during attacks, and preventive medicines like Verapamil if the episodes are frequent. It is important to identify and avoid triggers like stress, lack of sleep, alcohol, or strong smells, and maintain a regular routine. You should consult a doctor, preferably a neurologist, for an accurate diagnosis, especially if the pain is severe, one-sided, associated with eye watering or nasal symptoms, or persists for weeks, as early and targeted treatment can significantly improve your condition.