Tell Sam what happened
From Torg Adventure
You figure it's just too risky if you don't tell Sam about your not getting the condom on. You're probably going to impregnate her anyway, if you haven't already. By coming clean with Sam, you protect your ability to keep having sex with her as long as she will let you.
"Sam, you have to get off of me," you tell her. Sam has her eyes closed, and is slowly sliding up and down your cock. She still looks half-asleep.
"Don't you like this?" Sam seems a little confused, but keeps moving up and down on your cock.
"I love this, Sam. But you didn't give me a chance to put the condom on. We're not using any protection at the moment.
Sam's eyes open up slowly, but her slow motion continues. "Don't be silly, Max. I saw you put it on."
You're not sure why Sam is remembering things that way. She had been staring at the clock rather than your cock when she dropped herself down onto it.
"No, Sam, you didn't," you say a little more firmly. You hold up the still rolled-up condom in your hand.
Sam looks at the condom, looking more confused. She pauses her body over you at the top of her motion, most of your cock outside of her. She looks down between her legs, and sees your bare cock sticking into her. Then she takes one hand and touches the exposed skin of your hard-on, now coated with her wetness, confirming what her eyes have shown her.
"It's not like I came yet," you hurriedly assure your sister as she pulls her hand back. "Just get off of me, and I can put the condom on."
Does Sam freak, let you put the condom on, or does she just keep going?