It definitely sounds like you are in perimenopause and have been for quite awhile.  Your periods start to change when your progesterone levels drop...that also can be the reason for your migraines, esp. since they were coming before your period.  Progesterone also affects quality of sleep and mood balance.  The onset of hot flashes is usually one of the earlier indications that your estrogen level is dropping, too.  You don't want to be on Premarin which is a horse estrogen made from pregnant mare's urine and nothing like what your own body produced.  Talk to your doc about estradiol patches and Prometrium.  He/she should be familiar with both, and they are bioidentical, meaning they exactly mimic your own body's hormones and have few, if any, side effects.  They can really help to control or eliminate your symptoms.

Good luck, Suzi,

Sandy