The first time I ever masturbated until cum

The first time I ever remember cumming was a bit embarrassing ,
I`m not sure how old I was , probably pre teen , I had been talking with a friend about gay sex and how it involved putting your cock in another guys ass. My first thought was that my cock would get covered in shit and it would be a smelly mess. A couple of days later I was on the toilet when curiosity got the better of me.
I did a bit of shit in my hand and began smearing it on my cock , straight away I got harder than I`d ever been so using just one finger I began rubbing it in . I`m not sure how long it took , but I do remember my cock shooting its load all over my shit covered cock , balls and legs. I was in shock !
After feeling so awesome , I now felt so dirty and disgusting, I tried cleaning myself with toilet paper , but obviously did a lousy job as my mum told me I stank and to take a shower ,lol . Since then I`ve had a lot of anal sex both top and bottom and I often wonder did my first cumshot shape my sexual preferences or was I just destined to love anal.