What are some reasons for reoccurring and very painful migraines?

Usually no cause. Quite frequently it is hard to find triggers for migraines. Some causes include tobacco, alcohol esp. Red wine, skipping meals, too much caffeine or skipping caffeine, too much sleep/missing sleep, different smell different periods of menstrual cycle may trigger migraines.
Identify triggers. There are certain foods and aspects of lifestyle that can trigger or worsen headaches and migraines. The best way to identify triggers is to maintain a headache diary and keep a list of foods eaten before your migraine. Common triggers include chocolate, caffeine, cheese, msg, processed meats, alcohol, smoking/being around smoke, stress, skipping meals, lack of sleep or too much sleep.