Could This Be A Mis-Diagnosis?

So to sum this all up ive have had shoulder pain/burning/grinding/popping/locking etc for a year and a half. i went to a doctor he said it was Posterior Capsule Tightness. So i did physical therapy and it just made my shoulder worse, i go for an MRI monday but could anyone tell me what they think this could be? maybe a tear? could my doctor be wrong and its somthing more serious then just tightness? thanks!!