From your communication it appears that your doctor thinks you are suffering from migraine. Since you are apprehensive of a brain tumour, it would be good to get a CAT scan done so that your anxiety is removed once for all. Anxiety itself can be a cause of headache.
Flunarizine is indicated to prevent the attacks of migraine. It is not a curative medicine. It causes sedation i.e. sleepiness.
Divalpro (Zydus Neurosciences) is the brand name of a medicine called valproic acid (divalproex sodium). It is used in the prevention of migraine, epilepsy and mania. Apparently in your case it has been given to prevent the attacks of migraine.