I'm Experiencing Significant Pain In My Right Arm. There Is

I'm experiencing significant pain in my right arm. There is a very tender area at the shoulder, but the pain extends almost to my wrist. I can't lift it or put any pressure on it without pain. When I'm laying in bed, I have to try to keep it somewhat raised or the pain becomes unbearable. I don't recall lifting anything that was heavy, I didn't fall and as far as I can recall, I haven't over-exerted it. It's really pretty painful and since it's my right arm, it's somewhat incapacitating.