I've had my iPhone 5S close to 3 years now (will be in January). I was using it tonight, when the screen suddenly went black; it didn't show the rotating wheel like it usually does when the battery dies. I push the power button, and it shows the charging logo. I plug it in, and it immediately comes back on and starts charging from 8%. Typically, it doesn't do this, though I have noticed the battery does seem to die much faster than it used to. Is something wrong with my battery? Or is it just general wear on it?