Lie down and let her fuck you.

You slide into the bed and grab your girlfriend's waist and pull her on top of you. You put your hands behind your head and look down at your throbbing cock. Jess smiles.

"I suppose I'm going to fuck you now?" she asks. You nod smugly and she straddles you quickly, burying you into her. The feeling of warm, wet, silk surrounding the most sensitive part of your body is almost too much, and you stiffen, trying to hold back. Jess, sensitive to both your needs, stops moving, waiting for the moment to pass. When you smile at her and nod, she begins sliding up slowly, testing your reactions. You are able to hold off now, and you just lie back to enjoy the sensation. You make no effort to fuck Jess, testing her ability to remain true to the bet.

She is a gracious loser, and makes no effort to inspire movement, though she does seem to be getting tired. Her thrusts are less forceful, and her body is flushed. You realize that you can let go at anytime, but there's always Jessica to consider. She wants to get off, too.