Endometriosis: This condition, where tissue similar to the lining inside the uterus is found outside the uterus, is a common cause of chronic pelvic pain in women. It often presents with cyclical pain that can be severe and is associated with menstrual irregularities, dyspareunia, and infertility.

Adenomyosis: Similar to endometriosis, adenomyosis involves tissue similar to the uterine lining growing into the muscular wall of the uterus, leading to painful and heavy periods.
Ovarian Cysts: These are fluid-filled sacs on the ovary that can cause pain if they rupture or if they cause the ovary to twist (torsion).
Pelvic Inflammatory Disease (PID) without obvious infection signs: Early stages or mild cases of PID might not present with the typical signs of infection like fever or discharge.
Irritable Bowel Syndrome (IBS): This gastrointestinal disorder can cause abdominal pain, changes in bowel movements, and other symptoms that might be perceived as pelvic pain.
Interstitial Cystitis: A condition causing bladder pressure, bladder pain, and sometimes pelvic pain, which can be persistent and debilitating.

Ectopic Pregnancy: Although less likely if there's no obvious infection, an ectopic pregnancy is a life-threatening condition where the embryo implants outside the uterus, often causing severe pelvic pain and vaginal bleeding.
Ovarian Torsion: A medical emergency where the ovary twists around its ligaments, cutting off blood supply, and can cause sudden, severe pelvic pain.
Appendicitis: While more commonly associated with right lower quadrant pain, appendicitis can sometimes present with pelvic pain, especially if the appendix is located in a retrocecal position.

Uterine Fibroids: While not uncommon, large fibroids can cause pelvic pain, pressure, and other symptoms, but they are less likely to be the primary cause of lower pelvic pain without other symptoms like heavy menstrual bleeding.
Pelvic Congestion Syndrome: A condition characterized by chronic pelvic pain associated with ovarian varices, which are similar to varicose veins in the pelvic area.
Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis can cause chronic inflammation of the gastrointestinal tract, leading to pelvic pain among other symptoms.