I have a chronic back pain for the last three or two years . can you give me some ideas of what it could be?

Low back pain is mostly caused by injury to a muscle (strain) or ligament (sprain). Common causes include improper lifting, poor posture, lack of regular exercise, fracture, ruptured disk. You should use alternating hot pads/cold pads, and pain relief. Since your symptoms have lasted so long, you may need to see a Dr. It could be that you are not allowing for the strain to heal or something worse.