It was late at night and my boyfriend, Mark, and I had just finished another long, arduous day of work. As we climbed into bed together, our routine kicked in; kissing deeply, exploring each other's bodies with eager hands. Tonight, like every night before sleeping, I felt the familiar stirrings deep within my bowels. My ass was already sore from sitting all day on a hard chair, but that only excited me further. Mark sensed my excitement and knowing what I wanted, he skillfully lifted my legs up onto his shoulders, spreading me wide open for him. His thick fingers traced circles around my puckered anal ring before slowly pressing against it. "Tell me what you want," he growled into my ear. The words came out in a desperate whisper: "I want you to fuck me, Mark. Fill me up with your big cock. I want to feel it stretching me wide open." Mark's cock, already strong and hard, pushed against my entrance teasingly before attempting to slide inside. The intense sensation of being filled up like this never failed to excite me. As he pushed deeper, the walls of my ass clenched around him in response to the overwhelming pleasure-pain that surged through me with each thrust. He made love to me roughly, his hands digging into my hips as he pounded away at my tender, virgin hole. The sound of skin slapping against skin echoed around us, and I couldn't help but moan loudly every time he drove himself deeper inside me. With every thrust, I could feel myself getting closer to that inevitable moment when I would finally release - when all those uncomfortable feelings from sitting on that hard chair would be washed away by the warm, messy flow of shit that would coat both our bodies. Just as I was about to lose control, Mark pulled out suddenly, leaving only a trail of his sticky precum on my rim. He pulled my legs down, his hard cock still leaking onto my inner thighs. Smiling wickedly, he grabbed a towel and wiped me down clean, preparing for what was to come next. "Get ready, babe," he whispered, his voice hoarse with excitement. "It's going to get really dirty from here on out." And with those words, he pushed his thick cock back inside me, penetrating me completely once again. The sensation of being fucked so hard and so deeply made me shudder with pleasure as he worked his way towards that inevitable release – a release of both our tensions and fluids, as our bodies became united in a way only true intimacy can achieve. We rocked together wildly, our passed out bodies entwined in a sweaty, orgasmic dance. And then, with one final push, Mark buried himself to the hilt inside me as my body released a torrent of hot, sticky shit onto his skin. As the last wave of pleasure washed over us, we collapsed onto the bed together, spent and sated, our dirty fantasy becoming a reality once again.