I understand. It's so hard to shake those feelings. Try and remember that emotional reasoning is a cognitive error. Our anxiety makes us feel things, suspect things, fear things. And then, just to be a jerk, the anxiety makes us believe that because we feel something, it must be true. I can't know about your complete medical diagnosis, but the one thing I can say for sure that's "wrong" with you, with me, with everyone else here, is that we all have anxiety disorders that make us think things that aren't reality. Hang in there, and remember that you are suffering from anxiety. Like you said, when you aren't thinking about it, it feels pretty regular. Your arm didn't change, your thinking did.