Sex with my dog... ashamed

Once, I had just got out the shower, and was getting changed in my room...my dog was there but I figured...its just a dog it wont care.i let go of my towel.but felt some thing go up...you know up my anal hole.and realised my dog was haviung sex with me.i pushed him off me and I havent touched my dog in months, my mum and dad wont get rid of it.i havent told them what happened.i think about it every day and some times cry...i hate what i've done.