What is causing low-back, pelvic and abdominal pain for me? I am a 55 yr. old perimenpausal female and had all the OB-GYN tests, including a pelvic ultrasound in Dec. 2012. I, also, have had a colonoscopy and endoscopy done on Dec. 31, 2012 and was diagnosed with GERD. I am on 30 mg. Lansoprazole daily. My last menstrual pd. was in mid-Dec. 2012. I just got done having severe left side pain with alot of gas and bloating. The back pain gets so bad that I had to quit a job that required hours of standing. BUT, now the back pain is there when I sit , also. Any ideas what I should do?? Thanks!