This, according to the data scientists at Clue, may be a sign that you're not actually experiencing a period at all. Significant clots and the presence of gray-colored tissue can indicate that you're experiencing a miscarriage. "When a miscarriage occurs very early in pregnancy (for example, less than or equal to two weeks after an expected period)," the scientists tell Bustle, "it can be difficult to tell the difference between a normal menstrual period and miscarriage, especially if a person occasionally or regularly experiences heavy or painful periods."

But, they add, "the later into a pregnancy a miscarriage occurs, the more it will differ from a menstrual period. Bleeding from later miscarriage will contain fetal tissue, and blood clots will likely be larger than during normal menstrual periods. The tissue will likely look different from menstrual blood in color (ex. gray), consistency/texture, and shape."

If your period or a period-like bleed is accompanied by severe pain from your pelvis to your shoulders, along with abnormal bleeding, the Clue scientists say, you need to seek medical help immediately. "These could be signs of an ectopic pregnancy (when a fertilized egg attaches and grows somewhere other than the uterus, most commonly in the fallopian tube)," they explain. "Ectopic pregnancies are life-threatening and should be treated as medical emergencies." The phenomenon is rare, but it needs to be treated immediately using either drugs or surgery to remove the ectopic pregnancy from the body.

If you have heavy flow that isn't usual for you, it's something that needs to be checked out. The Clue scientists point out that it can be a sign of miscarriage as well, but it may also indicate other issues, from endometriosis, where uterine tissue grows outside the uterus and "sheds" painfully during each menstrual cycle, to problems with uterine fibroids or polyps, your body's reaction to an IUD, or a hormonal imbalance that's causing excessive bleeding. Anything that's abnormal for you needs attention.

"Symptoms of both menstrual periods and miscarriage can include heavy bleeding, pain, and cramping," note the Clue scientists. Outside of that possibility, though, particular types of unexpected cramps can signify different health issues. A sharp pain on one side, for instance, might indicate that you have an ovarian torsion, an extremely painful condition that involves the ovary's blood flow being cut off. Seriously agonizing cramps may also indicate that you've developed fibroids in or around your uterus, creating more pressure on the lining and more problems as the uterus contracts to attempt to dispel its waste.

Whether you've never really experienced blood or you suddenly notice there isn't any, this is a concern. "If it’s been more than two and a half years since breast development started and you are having symptoms of a period but seeing no blood, it’s time to head to your healthcare provider for assessment," Dr. Molly O'Shea explained for tampon brand Kotex. "Very rarely a girl can have periods and not see blood come out of the vagina because the hymen isn’t open." If you've had a period with blood before, a bloodless period might indicate over-exercizing, sudden weight loss, polycystic ovarian syndrome, or be a side effect of a new contraceptive.

You should not be feeling feverish or miserably ill while you're on your period. That is not normal, and it could indicate an infection, like pelvic inflammatory disease, which is often contracted via sexually transmitted illnesses and involves infections of the reproductive organs. It can also be a sign of the rare condition known as toxic shock syndrome, which can be associated with tampon use and needs immediate medical attention. Whatever's happening, a fever of more than 102 degrees while on your period needs a GP or emergency room visit ASAP.

If you suffer from serious pain while pooping on your period, it can be a sign that you have bowel endometriosis, in which the uterine tissue affects the bowel specifically and is shedding during the period. Rectal pain during your period from this condition can also occur when you're not on the toilet at all, which is extremely unhelpful. Endometriosis is a serious health condition, so if you feel embarrassed about talking about your butt, take a friend or supportive family member and find a healthcare provider who makes you feel comfortable. (Trust me, they do not care — and they do need to know.)

Some of us can feel uncomfortable or hesitant in divulging period details to our doctors or gynecologists, but we shouldn't. They're signs as to what's happening in our bodies, and there are certain period symptoms that act as big red flags (pun intended) that shouldn't be ignored or set aside.