My older child keeps saying ouch everytime I take off her diaper. I feel bad but i cant figure out whats hurting her. Shes 25 months. Theres no visible rash and shes grabbing the top of her butt cheeks/tailbone area. Diaper is not tight at all and haven't changed brandd of anything recently. And it's only when taking off the diaper. Otherwise she has no pains there. Hmmm?