What Causes Arm And Shoulder Pain Suddenly?

I am having pain in my right arm and shoulder all of a sudden and even into the right side of my neck. I have had a lot of trouble with my pain in my right shoulder blade the last month or so, so it could have something to do with that. I am not having any pain in my chest or left arm. The pain feels like extremely sore muscles but came on suddenly. I am a 47 year women with Diabetes. Just want to make sure it's not a heart attack.