First- if you are 14 years old, I hope you have an adult that can help you with advice and care. Any information I note to you needs to be considered with a guardian.
Your back pain could be from a number of sources. See “Back pain in the child athlete” to understand what can cause this pain.
Pars fractures are not uncommon in a young man with an incidence of one in twenty. If however you have noted degenerative disc changes on the MRI, this is more likely than not the source of lower back pain. X-rays and CT scan are more effective than MRI to note these fractures. It is not unheard of to have pars fractures associated with degenerative disc changes.
Braces can be helpful if the fractures are new. See “Pars fractures” on website to understand how these can be treated.
Dr. Corenman