Hello: The most common unilateral headache (half of the head) pain is migraine. It presents as a pulsating pain, with nausea or vomiting, light, sound and movement intolerance. Can last 4 to 72 hours. It can be treated with propranolol (the one you were prescribed) as prophylactic medication, but maybe it will not be enough. If you are having migraine, maybe you will need treatment for the acute attack. You can start with over the counter medications as Ibuprofen or naproxen. Other option (more specific for migraine) are the triptans as zolmitriptan, sumatriptan, eletriptan. There are other prophylactic medications if you are not tolerating propranolol, as topiramate, amitryptiline, semisodium valproate (not recommended if you are a woman). Try the common non-pharmacological measures: sleep well, stay well hydrated, avoid fasting, sleep deprivation and some foods as smoked fishes, cured meat, aged cheeses and alcohol; avoid heat and direct sunlight to the head (wear a hat or an umbrella). Avoid cigarette smoke, and if possible avoid stressful situations. Write a headache diary with all your pain characteristics (symptoms, frequency, duration, response to treatment and possible triggers). I suggest consulting with your doctor or a neurologist for a complete assessment. I hope this helps. If you have any doubt before your appointment, please let me know.