20F I fucked my sister's fiancé in her bed the night before their wedding

She asked me to help set up the venue the day before but I got there early while she was still at the salon. Her fiancé was alone in the house finishing some last minute things. I'd always caught him staring at my legs when we were all together and the tension had been building for months with stolen glances and brushed hands. That afternoon I wore the short sundress she hated because it showed too much cleavage. He offered me a drink to cool off and we ended up in her bedroom looking at the wedding dress hanging on the door. I said it was beautiful but I bet it would look better on the floor. He laughed nervously but his eyes darkened. I stepped closer, ran my fingers down his chest, and he grabbed my wrist hard. Next thing I knew he had me pinned against the wall kissing me like he'd been starving for it. His hands shoved my dress up around my waist and ripped my thong to the side. I was already soaked. He dropped his pants just enough, lifted one of my legs around his hip, and thrust in deep in one rough push. I gasped into his mouth, nails digging into his shoulders. He fucked me fast and desperate against the wall, the wedding dress swaying next to us like a ghost. Every thrust made the headboard tap the wall softly. I wrapped both legs around him so he could go deeper, my back scraping the paint. He groaned low in my ear how tight I was, how he'd jerked off thinking about this. I clenched around him hard when he hit that spot over and over. When I came I bit his neck to stay quiet, shaking so badly he had to hold me up. He pulled out right before he finished, came on my stomach in thick hot spurts while I watched his face twist. We cleaned up quick with tissues from her nightstand. He zipped up, kissed me once more, slow and guilty, then left to go back downstairs. I fixed my dress, wiped myself clean with her fancy hand towel, and walked out smiling like nothing happened. The next day I stood next to her at the altar in my bridesmaid dress, still sore between my legs, watching him say his vows while his cum from the day before dried on the inside of my thigh under my skirt