For years i've had right shoulder blade pain. it is now radiating down my arm and causing tingling in my fingers.what could this be?how is it treated?

Sounds like a nerve : maybe affected..you should get an MRI to see exactly what the problem is before we can recommend a solution

Upper extremity pain: upper extremity dysesthesias can occur for a variety of reasons. Most often these can be treated with intensive physical therapy. As long as radiologic workup inclusive of a cervical and shoulder MRI are normal good outcomes are achieved with therapy. Sometimes the use of oral medications and injections can be helpful in overcoming symptoms.

Pinched nerve: A pinched nerve can cause neck pain headaches, and pain or numbness running into the arm. There are other potential causes, however, and so it would be good to just get a regular check up to make sure it is nothing else. An MRI can confirm the diagnosis. Therapy, chiropractic, and interventional pain management are the non operative treatments for it if it doesn't get better. Thank you.