What can i do?! why does my middle to lower back feel like its going to snap in two?

Spinal work-up: Sounds like you would benefit from a complete evaluation with a spinal expert's history and examination, and perhaps starting out with some x-rays and physical therapy focused on those areas with a home exercise/stretching regimen. IF those not reveal or correct the issue, then an MRI may be in order as the next step to figuring out the problem.