Chronic pelvic pain is a condition which occurs underneath the belly button. It may be a symptom of several different conditions, but in many cases it is called neuropathic pain because the irregular functioning of the nervous system is the cause of this chronic condition. Usually this pain lasts for at least six months.
Causes of chronic pelvic pain
Chronic pelvic pain can be caused by a range of gastrointestinal, musculoskeletal, gynecologic, urological and body-wide problems. It may or may not be related to menstrual periods.
Gynecologic causes
Gynecologic causes of pelvic pain include Endometriosis, Pelvic inflammatory disease and Pelvic adhesive disease
1. Endometriosis
Endometrium is a tissue lining the inside of the uterus. In endometriosis condition the endometrial tissue is also present in the outer side of the uterus. Some patients with this condition will not have any symptoms, while others feel marked uneasiness and pain.  
2. Pelvic inflammatory disease
It is an acute infection generally caused by a sexually transmitted microorganism. Ruptured appendix, diverticulitis or tuberculosis are some other causes of this infection. Pelvic inflammatory disease can cause chronic changes in the uterus, ovaries and Fallopian tubes and permanently damage them, thereby causes the chronic pelvic pain.
3. Pelvic adhesive disease
This condition refers to the action of an abnormal tissue (adhesions) that causes internal structures such as the ovaries and Fallopian tubes to adhere to one another. These adhesions are tissues produced due to abnormal effects to surgery, infection or inflammation.
Other causes
Non-gynecologic causes may be associated with the urinary system, digestive system, pain in the muscles and nerves in the pelvis.
Gastrointestinal condition
Example, Irritable bowel syndrome, characterized by chronic pelvic pain with loose stools, more recurrent bowel movements with beginning of pain and pain relieved by defecation, without any specific cause.
Urologic- painful bladder syndrome and interstitial cystitis (pbs/ic)
PBS/IC is a type of bladder pain that is not caused by infection. Urgency and frequency of urination are high in patients with this condition.
Diverticulitis
A sac-like projection forms in the muscular wall of intestine is called a diverticulum. Diverticulitis is a condition occurs when diverticula become inflamed. This will lead to abdominal pain, nausea, vomiting, constipation, etc. and most often causes acute abdominopelvic pain. Chronic pain is not generally caused by it.
Pelvic floor pain
Symptoms are pelvic pain, pain with urination, pain with intercourse, frequent/urgent urination and constipation.  Tight, tender or band like muscles that supports the pelvic organs and hips, indicate that pelvic floor dysfunction could be contributing to pelvic pain.
Abdominal myofascial pain
In this condition the pain is originating from the muscles of the abdominal wall due to myofascial pain. This problem generally has some trigger points (small, localized areas of abnormal softness of the abdominal muscles).
Fibromyalgia
It is a chronic pain disorder that affects the muscles, ligaments and tendons. Women with this condition feel fatigue, headaches, sleep and mood disturbances.
Diagnosis of the cause of chronic pelvic pain
It is sometimes very difficult to specify the cause of chronic pelvic pain as it is caused by a number of different conditions.
Some of the diagnostic methods are
i) History and physical examination
ii) Laboratory tests (WBC count, urine analysis, etc.)
iii) Pelvic ultrasound
iv) Laparoscopy