I Have A Severe Pain In My Left Upper Arm

I have a severe pain in my left upper arm about a sideways hand measurement down from the shoulder. I have not performed any lifting, exercises, or other physical reason for it to hurt. I have troubles lifting my arm or moving it in way. Sometimes just resting it makes it hurt. I am 54 yrs old and have no medical conditions what so ever. What could this be from? I have put Icy Hot on it and even took 3 - 220mg of Aleve; neither worked. This has gone on for two and a half days. Today it is worse and nothing relieves the pain. Thank you, Dora