With your legs pulled against you, your aunt's cock is left with nothing to penetrate. Still mostly asleep, the head of her cock presses against your balls, rubbing back and forth across them intently. Her grip adjusts, pushing you down against her hard member, looking for any kind of stimulation she can get. This leaves you in a not-inconsiderable amount of discomfort, and you curl up more tightly, trying to keep her from crushing your balls with her heavy dick. Now almost in the fetal position, you find yourself pulled completely under the blankets, her hard cock now being dragged between your cheeks, sliding along your asshole with penetrative intent.
Deciding that enough's enough, you open your mouth to shout just as your aunt's hips buck, pushing her heavy rod directly into you, the words dying in your throat. Her strong arms keep your back pressed against her breasts as her pelvis slams into your ass again and again, thick cock scraping along your colon and thumping into your prostate. Your asshole burns from the friction, and your much smaller prick stiffens, bobbing along with the impact of her balls against yours. She groans cutely in your ear, though you're a bit too far gone to hear it, the feeling of her fat piece of meat in your ass becoming your whole world. With a weak cry, your body stiffens, and your dick spasms, a trickle of cum spurting onto your sheets.
Slamming her cock as deep inside you as she can, your aunt erupts as well, pumping her thick sperm into you. The dense, jelly-like ejaculate fills your ass, unable to escape around the tight seal of her cock, flooding your entrance before oozing further in. Your aunt, having finally cum, resumes her peaceful rest, still grinding against your ass, her now flaccid member lodged deep inside you.