I first pood my pants when I was 14. I held it all day at school and when I got home the house was empty. I'd often fantasized about doing it in my pants but never had the time or privacy to get away with it. Well now was my chance. I didn't want to mess my school clothes up, so I took everything off and I pinched a pair of my sisters used knickers from the washing pile. They had some skid marks in them but I didn't mind as I was about to do a lot worse. I saw her school uniform on the floor and I thought it would be so hot to wear it while I pood myself. I put everything on including her tie and blazer and walked around the house holding my bum and moaning about how deserate I was to go. It was so sexy and I rubbed my cock through her skirt untill I almost came in her knickers. At that moment I felt my poo moving and I didn't even try to hold it. I felt the heat of my load around my bum as I filled my sisters knickers and it exited me so much I couldn't help cuming in in them. It was a glorious feeling to be totally pooing myself in my sisters school clothes. When I finished I took my sisters clothes off and left them on the floor so she wouldn't know what I'd been up to and emptied my poo from her knickers into the toilet and rinsed them out in the sink and hid them behind my wardrobe.