You reassure her

"Hush Emily, be calm," you say soothingly, bending kiss her gently. "You're not likely to get pregnant the first time."

"But I could! And I'd be in so much trouble!" she says anxiously.

"You go to the bathroom and scoop it out and rinse yourself. That will help. But if you want to keep doing this you better get on birth control."

"Umm...you could...wear something...couldn't you Mr. Sharp?"

"But that wouldn't feel as good Emily. For either of us. You want to feel like this again, don't you?"

"Yes...yes Sir," she says obviously still worried. "But my parents would be really mad if they knew I was on birth control. They sent me to an all girls school because there weren't any boys here."

You smile at the thought of her parents delivering this naïve young morsel to you and kiss her gently again.

"You're an adult Emily. You don't need your parent's permission to get birth control. You're a big girl now."

"Yes Sir!" she giggles happily, squirming under you. "You made sure of that! You made me a real woman! Thank you so much Mr. Sharp."

"You're welcome Emily," you smile. "Now you better go to the bathroom and clean up. We'll do this again soon, I promise." You pull out of her, seeing thick curds of your cream ooze out of her pussy before she straightens her clothes and stands up with a smile. You kiss her again and pat her on the ass as she scampers for the door, looking back at you with a happy grin as she leaves.

You smile to yourself as you finish straightening your clothes, amused at her gullibility, and not caring for a moment whether you've knocked the stupid little bitch up or not.