As you assume the position behind your girlfriend, you can't help but feel like a dog in heat. The primal urge to claim her, to fuck her hard and deep, consumes you. With a grunt, you plunge into her, your cock slamming against her cervix, making her yelp in pleasure. You set a relentless pace, your hips smacking against her ass, the sound of flesh meeting flesh filling the room. Your girlfriend's cries of ecstasy push you closer to the edge, your balls tightening as you ready for release.