Everyone experiences varying degrees of flow during their period. You might have a shorter period with a heavy flow, or a longer period with a lighter flow. But if yours is so heavy that you're going through tampon after tampon, let your doctor know.

"Pelvic pain, heavy periods, back pain, and pain during intercourse — these symptoms, which many women experience during their periods, can often actually be signs of a disorder called endometriosis," Kate Shkodzik, MD, OB/GYN and medical advisor at Flo Health, tells Bustle.

This means endometrial cells, which should be located in the uterus, have begun to grown outside the uterine cavity, Shkodzik says. "Women who have endometriosis experience a variety of symptoms commonly associated with menstruation," she says, "and often do not receive a diagnosis until they try to conceive as the disorder can also impact fertility."

If you have period pain and your cycles are irregular, it could be a sign of something called polycystic ovary syndrome (PCOS). "PCOS is associated with an upset hormonal balance, including increased production of sex hormones [known as] androgens," Shkodzik says.

Other symptoms of PCOS include an absent period, hair loss, and acne. "Five to ten percent of women all over the world ages 15 to 44 have PCOS," Shkodzik says, but there are many ways to decrease the effects of the condition, if it turns out you have it

"Cramping or pelvic pain that accompanies your period that is not relieved with rest or ibuprofen (or any OTC) medication is concerning," Mary E. Fleming, MD, MPH, a specialist in obstetrics and gynecology, tells Bustle. While some cramping is fine, if your pain is so bad that you're not able to go to work, or go to school, or participate in normal activities, Fleming says you need to let your doctor know.

"There is normal pain and then there is severe pain which is something called dysmenorrhea, which typically needs to be treated," Fleming says. "And there are other conditions related to the system like endometriosis or adenomyosis, which can cause pain with periods."

"Pain that comes throughout the month and not just with [your] period, or involves changes in bladder or bowel habits, is also outside of normal," Fleming says. It's common to experience cramps and other aches and pains during your period, but if you experience these symptoms when you're not even on your period, it could be a sign of something more serious.

One possible explanation is pelvic inflammatory disease (PID), which is an infection of the reproductive organs often caused by a sexually transmitted infection (STI), like chlamydia or gonorrhea, Shkodzik says, adding that "PID can cause cramps not related to menstruation, abnormal discharge, and abnormal vaginal bleeding."

If you have back pain, along with heavy periods, it might be a sign of adenomyosis, which "occurs when the tissue lining of the uterus starts growing into the muscular uterine wall, causing pelvic pain, back pain, prolonged or heavy periods, and pain during sex," Shkodzik says. The good news is the condition is treatable, and usually resolves on its own as you get older.

Uterine fibroids might also be to blame for lower back pain. "Uterine fibroids are noncancerous growths that form inside the uterus walls and cavity and on its surface," Shkodzik says. "They may cause lower back pain before and during periods, prolonged or heavy menses, irregular bleeding, and cramps."

"Unrelenting or progressively worsening pain or cramps or bleeding warrant evaluation," Ginde says. This, again, can include pain that disrupts your day, as well as any pain that is severe, especially if you're older than 25.

As Ginde says, "Cramping in young women is very common, after age 25 it’s less common, and women who have had children experience cramping rarely. If cramping starts later in life, or the pain intensifies over time you should connect with your doctor for a consult."

"Cervical stenosis is a condition where the cervix is very narrow and impedes the flow of menstrual blood through the cervix, resulting in painful cramping in the uterus related or not related to menstruation," Shkodzik says. And since this is a condition you're typically born with, it may help explain cramps and pains that have gone on for years.

Keep in mind, though, that "slight changes in period cramps can be normal," Shkodzik says, so you won't want to jump to conclusions. That said, "you know your body best so consider visiting your doctor if you detect any unusual or sudden changes during your menstrual cycle," she says. That way you can sort these issues out sooner rather than later, and hopefully have less painful periods.