Periods spacing out to every four to eight months in your mid-forties, along with the fatigue, low drive and pelvic heaviness you're describing, fits the pattern of the years leading up to menopause.
Next Steps
A hormone panel along with a pelvic scan will confirm this and rule out other causes for the heaviness you're feeling.
Health Tips
Please mention your migraine medicine to your gynaecologist since some hormonal options can interact with it.