I Have Right Arm Pain, Especially When Laying Down For

I have right arm pain, especially when laying down for nap or all night long. when up for the day I notice it far less. at times it seems to originate at the elbow down to wrist and up to shoulder. sometimes feels it comes from shoulder blade. the left only hurts a little. I over extended my right arm only too far up and back last august pushing a tree limb up and back while on a lawn tractor. I also have had some tremendous life stresses for a year. I have been less physically exerting since then and still no better.