My parents left me home alone often when I was in my early teens to babysit my siblings. One day I told them to just stay in the playroom while I took a quick shower. I left the door open just a smidge so I could still listen for my siblings incase something happened but I could also shower. Well, as I got undressed, my dog came in and I didn't know. He was a pitbull, very sweet. I bent over to pick up my clothes and suddenly I felt a nose sniffing my lower region from behind. I turned around to see my dog but he threw his weight onto me and caught me off guard. I fell over and as I tried to get up, he mounted me. I tried to get him off of me but he was really strong and got aggressive so I just tried to relax. I had seen him play like this before with his toys and whatnot so I figured he wanted to play. That was until I felt something thick enter the tip of my vagina. At this age, I knew I had parts but I didn't really know the full extent to what they did, like things going inside them. I clenched my fists as I felt his cock go inside me. It was really thick. I didn't know what was happening but it hurt but felt good at the same time. I moaned a little as he began to thrust further into me. Suddenly I felt something build inside me and I started shaking, I screamed I started feeling fluid filling me up. My siblings came outside the playroom and I yelled for them to go back inside. My vagina started feeling tight and I looked down and saw my dog was suck inside me. I started to panic and tried to get him out of me but I couldn't. However, in the process of trying to get him out, I felt my clitoris. I started playing with my clit as we were tied and I started cumming over and over, squirting a few times even. Finally he pulled out and I felt his cum drip out of me. I'm embarrassed to admit that I unknowingly lost my virginity to my dog but at the same time, it was really great.