"Please," I begged and spied at my girlfriend's defiant glare. "I really, really, really need to." My brown-haired Lucy just shook her head and tapped my erect cock with a giggle.

"You may need to," she said firmly. "But I don't want you to. Not yet. And my needs come above your wants. We agreed that two weeks ago." I sighed and ran my hands through my hair as I stared at the patterned carpet.

"But..."

" ... but you've got blue balls?" She enquired sanctimoniously and cackled. She rubbed her hands and smacked the side of my thigh with a powerful hit, knocking me off-balance. "I can make them really blue. Black and blue." Her green eyes sparkled menacingly at me as she struck my other thigh, equally as hard, and turned the flesh a light shade of crimson. "If you think you've got blue balls, I can make them blue for you."

Her tone was angry and sharp; she looked piercingly at me and I could tell she was getting annoyed with my pleading. "But it's been twelve days," I countered. Even by Lucy's standards it was especially cruel. She had teased me every single morning, a few lunchbreaks and every evening rubbing up against me and caressing my body before sliding a well lubricated hand over my painfully erect cock and playing with me until I was about to come. And then stopping.

Her desire to play with orgasm denial on top of our usual play was getting too much. She might as well have bought me a chastity belt. "There are some men that have a vow of chastity," my dominatrix reminded me. "But I will be fair," she replied with a glint in her eye and picked up her phone. She tapped away at the keypad for a few moments, before removing her dress.

She was knickerless underneath; I knew this as I had met her at lunchtime in the park and she had openly felt up my crotch before slapping me on the thigh when I got too excited. She lay on the bed and glanced at the screen while looking up at me. "If you can tell me what the square root of one million, five hundred and twenty-two thousand, seven hundred and fifty six is, before I come, I will give you a treat," she said. "But you stay there, and don't move a muscle!"

I looked at her, startled by her wickedness. There was no way I could do a sum like that without a calculator (to be fair, I doubt I could have done it with a calculator), but she lay spread on the bed as her hands smoothed down her flawless body and nestled on the top of her vulva. She pressed a couple of fingers into her crack and cried out in pleasure, distracting me instantly.

"Feels so good," she cried loudly. "Feels so ... ohhhhh!" She smiled at my pained look; I knew her answer had to be above 1,000, but was struggling with my mathematical gymnastics. How could I concentrate when the Vagina Monologues was being re-enacted inches from my dripping cock? Sexual tension filled the room, as my perineum tingled and my balls ached painfully. I squeezed my muscles tightly and tried to look away, but the allure was too great. "Ahhh shit," she yelled and grunted, mewing with every pant.

I needed to watch her fingers rotating around her clit, it was calling me! Her breathing was snatched and ragged, groaning obscenely as her left hand squeezed her tits and she ground her hips into the soft mattress. My mind almost didn't comprehend what sums I was supposed to be doing; my focus was on the debauchery in front of my eyes.

She squealed, her legs spread lewdly as she revelled in the decadence of the moment. I could not resist and my hands inched towards my cock. I needed to play with myself, my balls ached in excruciating pain and they needed a release; I needed to be sated. I had had hundreds of erections in the previous fortnight and enough was enough.

My dominant girlfriend writhed on the bed, her legs thrashing as her fingers pressed on her pearl. Muskiness wafted to my nostrils as she rubbed her feet up and down my thigh, flicking my advancing hand away from my pleading manhood.

"Oh God! Oh God! Oh God!" She screamed; her vocal output was merely to torment me. "I'm coming!" She yelled, and threw her head back, emitting a loud, high-pitched squeal that seemed to echo around me.

I panted and gulped, my eyes transfixed on the masturbating woman in front of me. I needed that release; I pleaded with her again as she reached her happy place, but she ignored me. Her body wriggling and writhing as she tipped herself into a climax, screaming with wild delight and desire.

She looked at me, with a grin. "Well?"

"I don't know," I admitted; I had not thought about her question at all.

"Ahh pity," she called as she got off the bed, the wet patch prominent on the sheets. "Oh well, there was me thinking you did want to come."

"I do! I do! Please, I'll do anything." I got on my knees and pleaded to my awkward Lucy. "I'm begging you!"