Endometriosis: This condition, where tissue similar to the lining inside the uterus grows outside of it, can cause pain during menstruation, including pain during defecation due to the involvement of the bowel.

Dysmenorrhea: While primarily causing abdominal cramps, severe cases can lead to pain during defecation due to the intense uterine contractions and possible bowel involvement.
Constipation: Hormonal changes during menstruation can affect bowel habits, leading to constipation, which can cause pain during defecation.
Irritable Bowel Syndrome (IBS): Symptoms of IBS can worsen during menstruation due to hormonal changes, leading to abdominal pain and discomfort during bowel movements.

Ovarian Torsion: Although rare, ovarian torsion can cause severe abdominal pain that may worsen during menstruation and could potentially cause pain during defecation if the bowel is involved or if the pain is referred.
Ectopic Pregnancy: While less likely if the patient has regular periods, an ectopic pregnancy can cause abdominal pain that might worsen during menstruation and could potentially cause pain during defecation due to the location of the ectopic pregnancy.
Appendicitis: Although appendicitis typically presents with right lower quadrant pain, atypical presentations can occur, and the pain could potentially worsen during menstruation.

Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease or ulcerative colitis can cause chronic pain and discomfort during bowel movements, which might worsen during menstruation due to hormonal influences.
Bowel Endometriosis: A specific type of endometriosis where the bowel is directly involved, leading to cyclical bowel symptoms including pain during defecation.
Adenomyosis: A condition where tissue similar to the lining inside the uterus grows into the muscular walls of the uterus, potentially causing severe menstrual cramps and, in rare cases, pain during defecation if the condition affects bowel function or causes significant pelvic pressure.