Stress
The root of all physical illnesses is almost always stress – so do less of that! Stressing out throws off your hormones completely, enabling almost anything to change in your body over time. You may need a vacation (and strong drink) if you missed your period but haven’t made love.
The Thyroids
Your metabolism is regulated by the thyroid glands, which in turn cause your hormone levels to be majorly affected. Your menstrual cycle will suffer if your thyroid glands are over or under productive.
Birth Control
Your blood takes time to go back to normal after getting off the pill, which may cause you to think you’re knocked up. Contraceptives can majorly affect your cycle, so be weary of which sudden changes you make!
Weight Change
Of course your hormones change when you lose or gain weight suddenly…
Medication
Once again, your hormones will change if you switch your medication – as they all affect your cycle in different ways. Don’t freak out if you’ve recently stopped taking a pill…or two.
I’m Sick!
You may not ovulate if you’ve fallen ill during your scheduled period, so chalk it up to sickness!
Working Out
And there is a such think as exercising too much! Your period will be completely thrown off if you suddenly begin training for a marathon.