When I bench weights, my back bone plate kind of hurt, how can I avoid this?

It depends. Its not clear what you mean by your "back bone plate". If your lower back hurts when you lift weights, you should have it checked out. It may be inadequate padding on your bench, but spondylolysis is a condtion seen in weight lifters. Its caused by a stress fracture of the posterior elements that stabilize the spinal column. If you have that you should avoid lifting until its resolved.
Shoulder blade? I'll answer the question assuming you're referring to your shoulder blade . Bench press is a pretty unnatural motion. The mobility of the shoulder blade can be inhibited as you move your arms. This can be made worse if you have some degree of scoliosis which increases the side curve of your spine. I recommend more functional exercises using cables or bands. Even pushups are more functional.