Sometimes Balls can be like people, some get plump, and some don't(most will on your feeding schedule though). Check your husbandry on this Ball, if it's too hot, or it feels insecure, this could cause your snake to constantly move around. This could lead to it's apparent "triangle-ly" shape. BG knows what you mean, usually a snake is skinny when they look like this.
BG would keep an eye on it, it may be something internal. It couldn't hurt anything to take it to a QUALIFIED Vet and get a fecal done if you're really worried. That's the only way you're going to know for sure.