It could be your hardware. I had a L4-S1 fusion in 2005. I am still waiting to have the hardware taken out. I have spots in my back where the hardware is at that swell and turn a purple color. Some people develope an alergy to the metal. I know the pain. Mine started about 2-3 months out and has continued to get worse. I take Norco and it doesn't even touch the pain. Scar tissue also developes around the screws and can cause pain. What it is doing is pressing on area nerves. My surgeon wants to go in and widen the root canals and free up the nerves. There is nothing they can do for scar tissue itself. Good luck on getting some pain relief. When you do get an MRI make sure it is with contrast dye. They can see more with the dye.