I am having pain in my left back side right at the rib cage. This has been going on for months on and off but the last week and is consistent?

Check kidney. It is possible to injure the tissues surrounding the ribs, but you would likely remember the incident. The area you describe overlies the left kidney, as well as other organs. Kidney infections are not rare and can cause damage if untreated. This type of pain deserves evaluation by your doctor.