As her increasing arousal increases your excitement, you start to fuck her faster with harder strokes, bumping the base of your cock against her clit, trying every way to rub her g-spot as you fuck her.
Just as you get on the edge of your own orgasm, she gets more excited...
"That's it, slave," she says heatedly: "Harder! Faster! Yes! Yes! Harder! Faster! Oh, Yes! Yes!"
You pound into her desperately, trying as best you can to bring her off...