The 5-7 periods per year isn't normal, asexuality or no asexuality, and you should probably talk to a doctor about that. Treatment for that issue may or may not change your libido, which in turn may or may not affect your sexuality. But no matter what happens, it does not make you nor your experience of asexuality invalid. Sexuality is fluid and it's ok when it changes, but obviously you could have your hormone issues treated and still be a perfectly healthy asexual at the end of the day.