Based on the information you have provided here, particularly when you state that:
1. You have pain in your left side lower back and the pain goes down your left leg
2. When you wake up the pain is unbearable
3. Pain in the sitting position
This information leads to the possibility that you may have a disc herniation. A disc herniation is when the spinal disc (which appears between the bones in the spine) becomes compressed excessively on one side, causing the disc to be pushed outside of its normal position. Many times this situation can cause no symptoms, but when the disc presses on one of the nerves as they exit the spine, it can cause pain.
If this is the case, you may be noticing either sharp pain, or a numbness or tingling sensation as well. The pain may also get better throughout the day, and you may feel more uncomfortable laying on one particular side when sleeping.
The temporary relief position for disc herniations is typically either decompression of the spine, or laying face down and gently "propping' yourself onto your elbows, such as when a young child is watching television. This is referred to as the "sphinx" position. This position should not cause any increase in pain, and if so, do not perform them.
I may suggest that you visit your primary healthcare physician for an MRI. This will allow them to confirm the condition.
Sam Visnic
www.endyourbackpainnow.com/blog