Some women’s periods are like clockwork. They know, almost down to the hour, when to expect it each and every month. Other women are a bit less lucky, and experience irregular periods. Here are eight reasons why your cycle might be irregular.

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You’re pregnant
Chances are you’ll get to the bottom of this one pretty quickly. Pregnancy is one of the most common causes of an irregular or missed period (obviously), but even light spotting can happen in the early stages of pregnancy. It never hurts to take a test.

You’re breastfeeding
While lactating, your hormones are fluctuating a lot. That means that if you even have your period at that point (many women don’t get it back until they stop breastfeeding), your menstrual cycle will be pretty out of whack. Also keep in mind that some women, regardless of whether or not they breastfeed, will notice permanent changes in their cycles after childbirth.

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You just went on (or off) birth control
Here's the deal: When you go on birth control, it takes your body several months to adjust to the hormones, making your period irregular. Then, once you’re on the pill, your period could occur less frequently or stop altogether. Then once you go off the pill again, your period could take a few months to go back to normal, as your hormones rebalance themselves. (This is all normal.) Just remember: Pregnancy can still happen through any of this. Use protection wisely.

You’re on certain medications
Some prescriptions, specifically those prescribed for anxiety and depression, impact the body’s release of estrogen and progesterone (the hormones associated with ovulation and menstruation), which could mess up your cycle. Talk to your doctor if you notice irregularities, as it could be a side effect of your medication that you weren’t aware of.

RELATED: Here’s What to Eat the Next Time You’re on Your Period and Hating Life

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You’re really stressed
Cortisol, the stress hormone, also directly impacts how much estrogen and progesterone your body produces. When your cortisol levels are off the charts, you’re likely to have an imbalance in the other two hormones, sending your menstrual cycle into an unpredictable tizzy.

You have Polycystic Ovary Syndrome
PCOS is a hormonal disorder that causes tiny cysts to form on the ovaries, which interfere with regular ovulation. Common symptoms include irregular periods, hormonal acne and inexplicable weight gain, so if you notice any of these, consult your doctor immediately, as it could also increase your risk for infertility, miscarriage, diabetes and heart disease. 

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You’re a hard-core athlete
No, your period shouldn’t be affected by weekly spin classes and boot camps, but if you’re a high-level endurance athlete (like an accomplished triathlete or marathoner), it’s not all that uncommon for your menstrual cycle to be irregular or even stop for a while. Reason being, when you’re exercising at a high intensity for a prolonged period of time, your body wants to conserve as much energy as it can. And menstruating takes energy, so oftentimes your body will stop doing it to avoid losing that energy.

You’re about to hit menopause
The lifetime bookends of your period can be pretty unpredictable. Once you get it as a teen, it can take up to a few years for your period to get regular (#MiddleSchoolProblems). On the other hand, as you get closer to menopause, periods can be pretty irregular too, as your body prepares to stop ovulating and menstruating. Just relax and let nature do its thing.

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