Feeling her speed up and ram her hips backward onto his cock, he could barely control himself.  He picked up his own pace, telling himself in his mind "not just yet" as he grunted and plowed forward, his nuts slapping against her pussy.  The alternating sensations of being able to feel his prick sliding in and out of her anus with his fingers, and stroking her g-spot, and simply being inside her were almost too much.  He sighed softly in her ear, kissing the back of her neck again lightly.