She makes him an offer he can't refuse.

"You know... you can stay over if you want", Jessica says quietly, "it's much warmer inside, than running out in that rain."
Jessica looks at him with her deep colored eyes, obviously implying more. Jack quickly catches on: "Jessica, we can't risk it again, what if I got you pregnant."

In that moment, Jessica starts to smile and jump around in her short dress.

Jack, completley dumbstruck, looks at Jessica, jumping joyously around the room, " what are you doing babe?"
She grabs some water from the tap as she passes the kitchen sink.

Jessica jumps along the room over to Jack and latches on to his shoulders, whispering into his ear, "When I jump, I can feel all your cum sloshing around inside me. Do you really think adding a bit more is gonna hurt? I mean... there's really nothing you can do anymore, if you made me pregnant, it's already too late..."

"Now what do you say...", Jessica says, "are you gonna pump all that remaining hot, rich cum into your babe and fuck your pregnant girl for the first time?" Jessica hands him the glass of water, "I want all... this... inside...me."

Jessica is right, there is no extra danger in him fucking her again, draining every last drop Jack could possibly produce into her tight body. It's not like he can get her pregnant twice in the same day.