It can be tough to tell whether the pain's being caused by something simple or more serious. But these are 13 common reasons for it.
1. An Inflammatory Bowel Disease (Crohn's Disease or Ulcerative Colitis)
What it is: You get long-term (chronic) swelling and irritation in different parts of your digestive tract. It happens when something goes haywire in your immune system. It isn’t the same as irritable bowel syndrome (IBS). Crohn's can affect any part of your digestive tract (including your mouth). Ulcerative colitis involves only the large intestine (colon).
What the cramps feel like: It depends on the type of IBD you have. With Crohn's, you’ll feel cramps and pain in the right lower or middle parts of your belly. They can be mild to severe. If you have ulcerative colitis, the cramps will be on the lower left side of your stomach.
Other symptoms: Which ones you have depend on the specific type of IBD. They include:
What it is: If you haven't gone through menopause and still have your ovaries, you might get cramps mid-month, about 10-14 days before your period. This happens when your ovaries release an egg to ready your body for a possible pregnancy. The harmless twinge of discomfort is called "mittelschmerz," which means middle pain.
What the cramps feel like: You'll notice pain on one side of your lower belly. It lasts a few minutes to a few hours. It can be sharp and sudden, or you might just have a dull cramp. The side of the pain depends on which ovary released the egg. It may switch sides every month or strike the same place each time.
Other symptoms: There aren't any.
3. Ruptured Ovarian Cyst
What it is: A cyst is a sac of fluid. Sometimes they form on your ovaries. One type, called a follicular cyst, breaks open to release an egg and later dissolves in your body. If this doesn't happen, a different cyst can form. Most are harmless. But if one grows large, it could burst.
What the cramps feel like: A ruptured cyst doesn't always cause pain. If it does, you might have sudden, sharp cramps on either side of your lower stomach below the belly button. The location depends on which ovary had the cyst.
Other symptoms: You may also have some spotting. Before the cyst ruptures, you may feel pain or pressure in your lower belly, thighs, or lower back.
4. Pregnancy Pain
What it is: Your growing baby is attaching to the lining of your womb, or uterus. This is called "implantation pain," and it’s a sign of pregnancy progress.
What the cramps feel like: You might have a few slight cramps about 4 weeks into your pregnancy -- around the time when you’d get your period. If you aren't sure whether you're a mom-to-be, it's a good idea to take a test.
Other symptoms: There are none. If you're pregnant, you might start to feel queasy around the fifth or sixth week.
5. Ectopic Pregnancy
What it is: This is when a baby grows somewhere other than your womb. Most often it happens in one of your two fallopian tubes. It’s life-threatening for the mother and can’t result in a live birth.
What the cramps feel like: You may have mild cramps followed by sudden, sharp, stabbing pains on one side of your lower belly. The pain can get so severe that you also feel it in your shoulder and lower back.
Other symptoms: Before the cramps, you may have had typical pregnancy signs, like nausea and sore breasts. But not all women with an ectopic pregnancy have those. You might not even know you’re pregnant.
What it is: It's the loss of an unborn baby before the 20th week of pregnancy.
What the cramps feel like: They might start out like period pains, and then get more severe.
Other symptoms: You may have vaginal bleeding or spotting. Some pregnant women have these symptoms but don’t miscarry. But if you’re expecting and either one happens, always call your doctor.
What it is: This is a long-term (chronic) condition in which tissue similar to your womb's lining attach to other organs and begin to grow.
What the cramps feel like: They seem like regular period cramps, but they can happen any time of month. You may also have cramps and pain in your low back and stomach below your belly button.
See More: Guide to Endometriosis
8. Pelvic Inflammatory Disease (PID)
What it is: It's a bacterial infection that's usually spread by sex. It affects the parts that help you conceive and grow a baby. This includes your fallopian tubes, womb, ovaries, vagina, and cervix.
What the cramps feel like: You'll have pain on both sides of your lower belly and lower back. It can happen any time of the month.
Other symptoms: PID causes abnormal vaginal discharge and, sometimes, spotting. You might have pain or burning during sex or when you pee. Your periods might be heavier or longer. You might run a fever or have nausea and vomiting. You'll need to get the disease treated by a doctor.
9. Pelvic-Floor Muscle Dysfunction
What it is: Severe spasms happen in the muscles that support your bladder, womb, vagina, and rectum. It can happen after you have trauma with vaginal childbirth or after an injury, like a car accident.
What the cramps feel like: They're severe -- like sudden leg cramps in your lower belly. You may also have ongoing pain in your groin and back.
Other symptoms: You might have pain during your periods or sex, a burning feeling in the vagina, and problems pushing out stools. It could burn when you pee, or you may have a strong urge to go all the time. If you have these symptoms, see a doctor for a urine test to rule out a bladder infection. If you have one, the doctor will see bacteria in your urine.
10. Interstitial Cystitis
What it is: This long-term condition affects your bladder. Some doctors call it "painful bladder syndrome."
What the cramps feel like: You’ll notice them in your lower stomach (pelvic) area and in your genitals, along with pain and tenderness. They’ll get worse as your bladder gets full and when it's almost time for your period.
Other symptoms: You'll feel like you have to pee a lot, and it’ll be urgent. Sex might also hurt.
11. Irritable Bowel Syndrome
What the cramps feel like: They're sudden and in your belly. They might go away after you poop. Your specific pain will depend on whether you have constipation or diarrhea. You might go back and forth between the two or only have one type. Symptoms usually get worse during your period.
Other symptoms: You might feel pressure, like you tried to go, but couldn’t fully empty your bowels. You might feel sick to your stomach, have gas, or spot mucus in your poop.
What it is: It's irritation and swelling of a small pouch (appendix) on the end of your large intestine.
What the cramps feel like: You may notice pain around your belly button at first. Then, it gets worse and moves to the right lower side of your stomach. Cramps get bad fast, and they may wake you up. It could hurt if you cough, sneeze, or move.
Other symptoms: About half of people with appendicitis also have a fever, feel sick in their stomach, or throw up. Medical treatment is a must. A burst appendix can be life-threatening.
13. Ovarian Cancer
What it is: This type of cancer starts in the ovaries, the organs that make your eggs.
What the cramps feel like: Vague. You may write the pain off as something else, like constipation or gas. But the hurting and pressure in your lower belly won’t go away.
Other symptoms: Your belly may swell so much that you find it hard to button your pants. You might get full quickly when you eat and notice a strong, frequent need to pee. See a doctor if you have these symptoms for more than 2 weeks.
Always call a doctor if you have cramps that won’t go away. She’ll want to know if your pain is sudden or ongoing. The more details you provide, the faster she can diagnose and treat you. Get medical help right away if you have sudden, severe belly pain that continues to get worse.