Well, he's going to touch her more, then. Gently twisting the nipple with one hand and, also, what if he carefully gropes her breast with the other, palm against her nipple. How does that make her react? 

Soft whimpers and moans and wide reverent eyes and pressing herself into his hands and having to pull back a little before she overbalances and then pressing herself into his hands all over again and "please, sir, more? Please, sir, hurt me?"

If she's going to ask like that...

He shifts his weight a little so she can lean on him if she needs to, after seeing her nearly overbalance, and then gropes her harder with one hand, while pinching and twisting with the other? "Like this, slut?" he asks, grinning (and turned on, he wasn't feeling all that hard before but he is now!). Despite the vulgar language there's little heat in his voice, just amusement and care. 

"Yes sir," she gasps, "thank you, thank you sir, please, more—"

More? He can do more. He switches which hand is doing what, and gropes harder, squeezing flesh between fingers, and pinches with the other hand to get a good grip, twisting harder and further. He's very hard now. And having a very good time. 

Now she's just outright leaning on his hands and moaning and trying to thank him and failing because articulating entire words is hard.

Bringing her to the point where she's unable to speak is an incredible feeling. He twists and gropes harder, really enjoying the feeling of power over her and her emotions, watching the tears on the sides of her cheeks (those are okay right? Yes they are, he's pretty sure), watching her face and hearing her struggle to speak and moan instead, feeling her lean on him because she can't hold herself upright... and feeling her want it.  "You're going to be mine," he whispers to her, switching hands again to even things out. "My slave-in-waiting. Mine." (Yup, saying that turned him on even more.) He pushes harder, hurting her even more. 

"Mhm, mhm, yours," she manages. "Yours."

"Fuck this is hot," he tells her, giving up the semblance of order and evenness and just starts groping her, doing whatever he wants to her tits, because he can. "You're hot, your whimpers are hot, the way you want me is hot, the fact that you're giving yourself to me" fuck that makes his cock twitch "is really hot, touching you is hot, fuck." He grabs both her nipples and twists. "And you want this. Fuck." 

"Mhm, mhm, mhm," she agrees emphatically, nodding along to everything he says and especially to the part where she wants this. She's tearing up even more now than she did when he was playing with her clothespins, and shaking and swaying and half held up by his hands on her tits, breathing raggedly and making small high-pitched noises whenever he does something especially painful, her chest still thrust out toward him and her hands still, still, always, clasped together behind her back.

She looks beautiful like this. Entirely in his power, offering herself to him despite the pain, thrusting her tits into his hands, tears running down her cheeks... he wants her. He... hm, he can't actually let go of her breasts, can he. Not without her falling over, which he doesn't want. But maybe... leaving one hand steady on her breast to keep her upright, he slides the other up her shoulder and neck and face to the side of her head, still supporting her. And when that's done, he uses that hand to pull her in for a kiss, leaning down as he tilts her head up into his. 

She melts into the kiss, moaning softly, relaxing into his hands.

Fuck it feels so good how much she wants him. He kisses her harder, taking that feeling from her, making her feel how in control of her he is, his other hand idly groping as though he's remembered that it's there. John feels... good. Very good. (Also like he wants to fuck her. That should wait though, even if he's imagining it, seeing himself throw her to the floor and spread her legs and... another time. When she's his, for real.) 

Oh, she loves feeling how in control of her he is.

That's a very good thing, because he really enjoys feeling in control of her. And he enjoys the way she wants it, the way she thrills to it. He breaks off the kiss and stares down into her eyes. "Mine," he says, half growl. He wants to fuck her, but also he doesn't. What does he want to do? He wants to be more in control of her, to show her his control, but he's not sure how to do that at the moment. He gropes her tit with his free hand, kneading it while trying to think of what to do. 

"Yours," she breathes, shivering. "Thank—thank you, sir. Thank you for doing what you want with me."

Every word out of her mouth just turns him on more. The problem is, he can't just do what he wants to do with her. Not with the other things he wants. (He can't fuck her if he wants to make that fantasy they've had about taking her the first time a reality, if he uses her mouth he's wasting the opportunity to do the desk toy thing properly, if he stops... he doesn't feel like he can stop. Or should stop. Even if he did he doesn't know how.) "Anything I want," he says, tracing fingers over her cheeks and lips as he gropes her. (If only he could have everything he wants.) 

She kisses his fingers and leans into his touch.

"Mhm," she agrees. "Yours. Your slave-in-waiting. Yours to hurt and play with."

He hadn't expected her to kiss his fingers like that. And that gives him at least some of a idea. (Even if he really does like hearing her say all these lovely things.) He moves a finger back in front of her mouth. "Kiss it again," he tells her, his voice making it clear that it's an order. "Kiss it, and then suck on it, show me how much you want me." 

With a tiny whimper, she obeys, dedicating herself to sucking his finger the way she wants to suck his cock. Complete with swallowing it as deep as he'll let her.

He's a little surprised at her enthusiasm, but he'll let her swallow it deep. She wants him so very badly, and he's enjoying that sensation at the moment. He lets go of her face to get a better angle, and then starts sliding it slowly in and out, exploring the inside of her mouth and throat. 

She wants him so very, very badly, and is enjoying sucking on his finger and enjoying the way fresh tears spring to her eyes when she gets it deep enough. And she's steadier now that he's not hurting her as much, so she doesn't need him to hold her up.

That's good, because he's very much focused on his fingers and her mouth and her face at the moment. The sensation of his finger sliding into her throat to the point where she tears up again is incredible. Can he add an extra finger? Does that work? (Also, he's definitely wishing that it's his cock in there instead. Even if he'd rather do a different thing, damnit.)

He very much can add another finger, and she's just as enthusiastic about sucking and gagging on two at a time, and she's looking up at him in loving awe and gratitude while she does it.

She looks so incredible, starting up at him like that. And the way she's sucking on his fingers... it's making him want her to suck on his cock like that. (And how hard he is is also a factor.) Even though there's something else he wants to do instead. He just wishes things wouldn't keep going wrong! He pushes his fingers a little deeper into her throat in frustration, then pulls back immediately, feeling a little foolish. He sighs, and pulls his fingers out the whole way. "Do you want my cock instead, slut?" he asks her, voice a little less certain than he wants it to be.