My dog Charlie is coming up on 3. It's probably nothing, but when I touch the middle of his back, he scrunches it up, like he it tickles. I've also notice that the skin across his back gets very tight when he is ready to go outside to do his business. After he does, the skin is looser but he still will kinda scruntch his back up. So is this anything to worry about or is this just part of how he is made up. Oh and none is this is discomfort, or painful for him...it's just kinda funny to watch.