Why do I always have migraines?

Genetics vs Other. While you may simply have a predisposition to migraine headaches, it is important to rule out the possibility of other causes for frequent headaches. This is not only because some of these causes can be dangerous (e.g. Brain mass), but because many of them are treatable (e.g. Sleep apnea)! a neurologist can help to guide diagnosis and treatment.
See your neurologist. There is no easy answer. Certainly you should be under the care of a neurologist. It is not uncommon to have a history of migraine from a young age that persists. There are many effective treatments.
Get checked out. A good start at finding potential headache triggers would be to maintain a diary. Every time you have a headache write down what you were doing, the foods you ate that day, alcohol, smoking, caffeine, stress, how much sleep you had the night before, eye strain, etc. Try to find patterns in your headache so that you can learn what things to avoid. Get checked by your doctor.