Wow, is this ever the runaround! All you want is a diagnosis and those who are supposed to be treating you are making it impossible for you to get one. There can be no successful treatment without diagnosis! So without a diagnosis, what the heck is the PT treating you for? They should be doing exploratory therapy, looking at pain and range of motion, range of non-painful exertion, all the sort of stuff that might enable a tentative diagnosis and create a temporary treatment plan.
From the wiki:
Graston Technique is a therapeutic method for diagnosing and treating disorders of the skeletal muscles and related connective tissue. The method employs a collection of six stainless steel tools of particular shape and size, which are used by practitioners to rub patients' muscles in order to detect and resolve in the muscles and tendons. Practitioners must be licensed by the parent corporation (TherapyCare Resources Inc.) in order to use the Graston Technique trademark or the patented instruments
Several examples of Graston treatment have been used in contact sports where scars and contusions are common. However, the Graston Technique has not been rigorously scientifically tested and its evidence basis and assumptions are considered questionable at best. There are no high quality clinical trials that validate the efficacy of the Graston Techniques.
Sounds to me like an unscrupulous practitioner has got hold of you and wants your money or that of your insurance company. Doesn't sound at all like the treatment you probably require. You've probably torn something loose and this guy's fooling with it is making it much worse.
If you can't get anywhere with your doctor, there are boards of medical supervisors . . .