There are numerous factors that could be causing your headaches. However some headaches can be chemically caused such as a migraine, and some can be body related (cervicogenic, tension based). These styles of headaches often overlap and can lead from one to the other. So which one do you fit into?
Cervicogenic- generally it is pain that is located on one side that beings in the upper neck region and can radiate into the anterior parts of the head. It is of moderate intensity (where you can still function throughout the day) and is generally intermittent in nature (not continuous). Neck movements or sustained postures could cause such discomfort and there is normally some restricted neck mobility with tenderness over the upper neck muscles.
Migraine- this type of headache is generally not physically based rather your reaction to changes in your nervous system or your reaction to certain stimuli. (poor sleep, foods etc.). Generally a migraine is 5 or more headaches over a minimum of 4 hours in duration and has associated features such as nausea, vomiting, problems with light or sound, aggravated with exercise and has a high intensity pulsing.
Tension headache- can often be called a ‘muscle contraction headache’ thus is muscular based, where it often has tenderness throughout all the muscles of the neck. Generally this occurs on both sides of the neck, mild in nature, reproduced when pressing on the muscles, while exercise alone will not aggravate your symptoms.
By not treating one style of headache, this can often lead to the production of another style. If you do suffer with constant headaches, now is the time to act to relieve those symptoms once and for all.