A sinus headache is caused by the swelling and build-up of pressure in the sinus cavities behind the eyes. Symptoms are worse when you bend over due to the differences in pressure between the surrounding atmosphere and the sinuses, according to Harvard Health Publications. Continue ReadingSymptoms of a sinus headache include pain in the front of the head and face that is worse when you bend over and when you first wake up, says The National Institutes of Health. A sinus headache happens when there is a build-up of pressure inside the sinuses and the small opening from the sinuses to the nose becomes blocked. The pressure builds up and causes pain behind the face and head. Mild symptoms can be treated with rest, drinking plenty of fluids, over-the-counter painkillers and saline nasal sprays. You may want to see a doctor if symptoms persist after a week, get worse, or keep coming back, as stated by the National Health Service. Learn more about Conditions & Diseases