What changed? Did something happen to cause the pain. Do you have leg pain? Did you before the surgery. Do you have a rehab protocol with core strengthening and gentle stretching exercises? Are you following the protocol. Let the surgeon know what is happening. He/she will probably want to see you again.
Depends on several. Depends on why you had surgery & how extensive it was as well as what kind of shape you are in in terms of: obese, smoker, not exercising, doing things that put your back at risk & the possibility of ongoing changes in the spine that can lead to this . If your surgery was for disc herniation, there is a 10% chance of developing back pain due to further disc degeneration & 5% risk of reherniation.