Jon unzipped his pants, dropping them as well as his underwear. Where his penis once was, there was a slit, shaved, he realized with a shudder. "Well? Go on, Jon, it's not going to bite. I would know."
Another shudder. He reached down and spread the lips with his fingers, shuddering at the sensations running through his body just at that touch. He slid a finger inside for just a second before remembering his mom was right there. "Don't worry honey. I offered, remember?" Jon nodded, and slid his finger back in, exploring... forgetting again, rather quickly, that his mom was there as he felt inside, every inch.
Nothing mattered anymore but what his hand was doing, the ecstasy, the... utter wrongness of it all. "What the hell am I doing?!" He pulled his fingers out, trying desperately to ignore his mind screaming at him to continue, and the aching pain.
"You were masturbating, honey. There's nothing wrong with it." Mom smiled at him, sitting down on his bed and pulling his - now her - cock out of her pants. She looked at his crotch and started jerking off. His mom was jerking off to him! Probably to thoughts of boning him! He looked at her with disgust, wanting to just forget all of this...