When we suffer from Anxiety, basically any pain, twinge, tingle raises an alarm. When it's bad, so much of my anxiety seems to center around 'what is this pain in/near my chest, something must be wrong with my heart, im going to have a heart attack and die' no matter how minor the pain is that's where my mind goes. Not too long ago I had a pain that was in my shoulder, it wasn't severe, but it was there and hard to ignore, of course, like you, I assumed it was something to do with my heart. But it wasn't. You could have easily pulled a muscle and not realized it. I always try to remember how hyper alert my mind is to out of the ordinary sensations or pain and how quickly it jumps to worst case scenario.