The only thing worse than getting your period is not getting your period. The anxiety, the trip to the drugstore for a pregnancy test, and the confusion that sets in when the test comes back negative is worse than any case of cramps.

And while a lot of women don't talk about it, almost all of us have been there. Missing a period is very common, says Melissa Goist, M.D., assistant professor of obstetrics and gynecology at Ohio State University Medical Center. And luckily, most of the time, it's harmless and only your body's way of showing you some TLC. [Tweet this relieving fact!]

"When you undergo a lot of stress, your body may not ovulate and have a period," Goist says. "That's your body's way of protecting you from getting pregnant and having the additional stress of a baby." That stress could come from your job, your boyfriend, or even your workout. Excessive exercise-and the stress it causes on your body-can lead to missed periods. In one study, a quarter of elite female athletes reported a history of missing periods, and runners led the pack.

What's more, menstrual cycles can go MIA even if you're on a medication that's supposed to regulate them. Birth control pills and the Mirena IUD can make your endometrial lining so thin that sometimes there's nothing to shed, says Jennifer Gunter, M.D., an ob-gyn at Kaiser Permanente Medical Center in San Francisco. That's also true for 28-day packs of birth control complete with placebos and some oral contraceptives with placebo pills spaced further apart that are designed to make you only get your period every few months, she says. And it's fine, as your body isn't ovulating when you're on hormonal contraceptives anyway. If you discontinue use of BC, remember it may take six or more months for your periods to get back on schedule.

When to Worry

If the above doesn't describe you and your missed periods hit the three-month mark (when missed periods are officially dubbed amenorrhea), visit your gyno, Goist says. Several missed periods in a row can be a sign of decreased estrogen levels, which can spur bone loss, according to research in the Journal of Obstetrics and Gynecology. To your body, it's like going through menopause right now (but without all those calcium chews).

Even more concerning is that serious health conditions could be behind your MIA menstrual cycle. Among the most common is polycystic ovary syndrome (PCOS), a hormonal imbalance that makes ovulation infrequent or stops it altogether and that can increase the risk of endometrial cancer. "The uterine lining builds up every month but is not shed. Over time it can thicken and cancerous changes can occur," says Draion M. Burch, D.O., clinical assistant professor at the University of Pittsburgh School of Medicine. PCOS is the most common cause of female infertility in the United States, and while its exact cause is unknown, early diagnosis and treatment can help reduce the risk any long-term complications such as type 2 diabetes and heart disease.

Eating disorders and too-low BMIs can also cause missed periods. According to the National Institutes of Health, having a body fat percentage lower than 15 to 17 percent increases your chances of missing periods for an extended period of time. The body isn't in the shape to carry a pregnancy, so the brain tells your ovaries to shut it down, Gunter explains. And even if your BMI doesn't get too low, super-speedy weight loss can send your periods on hiatus.

Tumors, while pretty unlikely, can also cause problems, Goist says. Apart from missed periods, ovarian tumors can cause persistent bloating, pelvic pain, difficulty eating, persistent backache, constipation or diarrhea, extreme fatigue, and discomfort during sex. And while even less likely, it's worth noting that a tumor on the brain's pituitary gland-which regulates many of your sexual hormones-can cause amenorrhea. Brain tumors typically come with other not-so-subtle symptoms, though, such as nipple discharge and double vision, Goist adds. So if the missed periods don't send you to the doc, the other symptoms probably will.

If you do visit your gyno about a case of the missing period, it's important to go armed with a calendar of any menstrual cycles you have had, as well as a list of any other symptoms as well as health and lifestyle changes that have occurred recently, Goist says. And whatever you do, don't stress about it. It won't make your period come back any faster. [Tweet this fact!]