Fill 'er up.

Too late...
"Sorry, Tara, probably should have warned me earlier..." you grip her throat, and lace your fingers over her left hand with your other hand as you bottom out, and begin to pump hot semen into her spasming cunt.
"Fuuuuuckkkk...." she's moaning like a whore, and her eyes are rolling, but there's a whine in her voice as well..."no...no...you....can't...."
"Seems like I.....ahh!....am, though...." It felt too good, it was a runaway train, there was no stopping it.
"Oh my god...." she's panting now as you pull out, dribbling cum on her ass as you roll onto your back. You look sideways at her. Her face is a mess of different emotions: ecstasy, bewilderment, disbelief and fear.
"I...can't...." her lips starts to quiver... "I can't get...." she rolls away from you, curling into the fetal position.
"Hey, don't worry." you take her gently by the shoulders and turn her back around. "Jenna has some Plan B that she always keeps around just in case. Just go upstairs, swipe it from the medicine cabinet in my bathroom. You'll be fine." You hope that's true.
She looks into your eyes, tears brimming. "Really?"
"Really. You'll be okay. A little nauseated maybe, but you'll be okay. As soon as you get cleaned up, go get them." She nods, and pulls you down into a kiss.
"Thank you, James. I've needed that since the first time I saw you. Every one I've been with has been a punk, or a wussy little boy." She gives you an apologetic look, "Sorry. Didn't mean to talk shit about Jared."
"Hey, it's alright. He's a good kid and a smart kid, but he's got no ambition, and to be honest with you honey, he's got some issues being faithful."
She laughs. "Like father, like son?"
You suddenly realize the irony. "Yeah. Although, I've never broken my marriage vows before, Tara. You're the first."
"Oh."her face lights up with adoration. "So...I was special then, huh?"
In response, you gather her up into your lap. "Yes. I guess so. I wasn't expecting all this underneath. I thought you were just a little temptress." She rests her head against your chest, lacing her fingers together with yours.
"Thanks, James. I...picked up some bad habits from my mom. My real father bailed after he nailed her and got her pregnant with me. I don't even know his name. And for the most part, the guys she's hooked up with since have been...less than great at filling the role." She's nuzzling your chest now, and you can feel your own cum dripping onto your leg from her well-fucked pussy. You decide not to bring it up.
"I don't know how this is going to go, Tara." you decide that honesty is best. "I still love Jenna. I don't want to lose her."
"I don't either, James. I love her, too. I know that sounds weird, considering what I...what we just did. But it wasn't about hurting her." She looks up at you. "If...you tell me this won't happen again...I understand. I don't want to ruin your life." She's looking into your eyes, fighting to be brave in the face of the answer she expects is coming.