I got knotted by a dog

I was living with my girlfriend and we had a dog who stays outside , and one day my girlfriend left to visit , and at times I got use to masturbating when I’m alone , so I started to get horny stroking my cock , I was so horny thots coming around , i always wanted to to know how it felt like getting fucked in the ass , but no one around who was gay or I was to shy to do anything about it so I just make homemade dildos with socks gloves and condom to make it a hard cock and I got tired of fucking myself , and one day while my girlfriend was visiting ,
I was sitting outside horny thinking , and my dog was beside me , thots started racing how I would get fucked , and then it came to me that my dog has a cock and can fuck, so i brought him into my place and I went in and grabbed his cock and started stroking it , while I was stroking it kept getting bigger and he started thrusting his hips, so i went on all fours butt naked , and put him on top of me and I pushed his cock against my ass and he started thrusting , and he got off he kept getting off and I kept stroking and putting on top of me until I was to high for him so I went lower and arched my back and he thrusted hard 3 times and third time his knotted went inside as I was feeling good wondering what’s that in my ass I didn’t know he was inside me , and I was scared my girlfriend will come back so I pulled him out and it hurted and I saw him thrusting still while cum started coming out his cock , it was something I did and regretted it but was so horny my ass hole got sore a couple left of days , I was acted to try it again because I didn’t want to get busted , I wanted to try it again but was ashamed of myself , and I’m still thinking how I can get fucked this was 5 years ago that happened