Take a more hands on approach.

Without warning, you slip the tip of your thumb into the entrance of her ass, and a squeal escapes her lips as she feels her sphincter pop. She freezes and doesn't dare move, bracing herself against the wall. About a third of your cock is still embedded inside her pussy, and her ass constricts tightly around your digit.

"Back up," you whisper, your other hand reaching around and circling your fingers around her clit. She whimpers as she slowly slides down, at the same time backing her ass onto your thumb.

"Ooohh..." she moans when both your cock and thumb are entirely buried in her pussy and ass. You take your free hand and grab the back of her neck, forcing her to bend over even more. Off-balance, the full weight of her body presses up against the shower wall. The disparity between your heights and the size of your cock props her up, forcing her to stand on the tips of her toes.

“Oh my god!” she cries. “Oh, my goood...”

You start pounding away at her, and the sound of her moans sends vibrations through the glass pressed up hard against her face. You pump away, rhythmic and fluid, sliding in and out of her like a well-oiled piston. The shower wall rattles and wobbles, your combined weights slamming hard against it. You stare at the mirror mounted on the opposite side of the bathroom, watching the reflection of her breasts and face crushed flat up against the glass. The circumference of her pancaked tits expand and contract each time you push her up against the surface, and through the refraction of the glass and the fog in the air, it looks like some sort of grotesque impressionist painting.

“I love you…” she pants, her voice weak with pleasure. “I love you...”

“Mm… really? You won’t love anyone else?” you ask, stimulating her anal walls with the tip of your thumb.

“Ah… I… I won’t…”