A past Electroconvulsive therapy from many years ago is unlikely to be the cause of your current headache. Most headaches are due to common reasons like tension, stress, poor sleep, or neck strain (Tension headache). Try rest, hydration, proper posture, and you can take Paracetamol for relief. If the headache is severe, persistent, or associated with vomiting, vision problems, or neurological symptoms, consult a doctor for evaluation.