While at least one symptom of PMS affects 85 percent of women, severe discomfort or moodiness before your period could actually be a sign of something more serious. Some women spend years not realizing they suffer from endometriosis, polycystic ovarian syndrome, premenstrual dysphoric disorder (PMDD), or another major health problem because they've confused it with run-of-the-mill PMS.

If your period is wreaking havoc on your ability to function, don't dismiss the prospect of a more severe condition. Talk to your doctor if you notice any of these signs.

1. Spotting right before your period
Pre-menstrual spotting can be a sign of endometriosis, according to OB/GYN Shahin Ghadir, MD. This condition leads the tissue that normally lines the uterus to grow outside of it, spurring the development of painful cysts and scar tissue. It also can cause severe premenstrual cramps and nausea that are often confused with PMS. Other signs of endometriosis include heavy periods and pain during sex.

2. Acne or abnormal hair growth
Hormonal imbalances associated with PCOS (polycystic ovarian syndrome)—characterized by an excess of androgens—can lead to mood swings and other PMS symptoms before your period. But unlike standard PMS, they also can cause hair growth on the face or body, hair loss on the head and acne says Ghadir.

3. Progressively shorter periods
Noticeable PMS combined with menstrual cycles that get shorter and shorter can signify perimenopause—the transition to menopause. In women under 40, these symptoms can be a sign of premature ovarian dysfunction, which causes you to reach menopause early, Ghadir says.

4. Emotional issues that interfere with your life
If your mood swings get in the way of your work or your relationships, this could be a sign of PMDD, which includes mental health issues associated with PMS in a more severe form, according to OB/GYN Sherry Ross, MD. Debilitating mood changes could also be a sign of anxiety or depression. People with these conditions will probably experience them month-round, but they often intensify right before your period. If your PMS involves emotional problems so severe that you have trouble sleeping, getting out of bed, eating, or getting your work done, it could actually be a sign of depression.

5. Really bad cramps
Some cramping before or during your period is normal, but if basic activities like walking are painful or your cramps cause nausea, vomiting, or numbness in your legs, they could be a sign of endometriosis, says Ross. This condition can be easy to miss if you expect to be in pain during your period, but it's really important to spot early on because it can lead to infertility, ovarian cysts, and chronic pain.

6. Symptoms beyond the pre-menstrual phase
If any of your PMS symptoms seem to last after your period starts or begin more than two weeks beforehand, they likely can't be attributed to Aunt Flo, says Ross. If your bloating continues throughout the month, for example, this could be a symptom of lactose intolerance, irritable bowel syndrome, acid reflux, or an imbalanced diet.

While a bit of discomfort or irritability around your period is normal, it's important not to minimize or normalize anything more than that. If something seems like a severe enough problem to look further into, it probably is.