Why did i have sudden severe lower back pain and gass ?

Pelvic problem: Back pain rarely causes pelvic pain but pelvic problems often cause back pain. Sudden distension of the colon can cause pain in both areas. Symptoms could be simply due to constipation or dietary issues or even colitis. Many problems can occur with the same symptoms such as urinary tract infections, ovarian cysts, etc. See your family practitioner or gynecologist.