Figure out what's causing the headache. It could be sinuses due to the changing weather and allergy season. Could be from staring at a computer or TV screen for long periods of time. Could be from a too-tight ponytail.
It is caused due to many reasons, some of them is rise in BP, cynocytis, cold and cough, dehydration, high-grade fever, due to wrong medication, allergic, long time TV or computer watching or operating, chronic diseases, migraine, etc. Kindly contact your doctor ASAP.