Not exactly sure how old when I started playing around anally, but I couldn't have been more than like 12 or 13. I heard some friends of mine talking about girls being able to "do it up their butt" too
. So during masturbation, I would try playing around with getting a Sharpie in there. I think it took a few sessions before I was brave enough to put something all the way in, but once I did, I got this weak feeling in my knees and the rest is history. I've masturbated that way ever since.
I didn't have anal sex until I was 19 and in college. I had a particularly adventurous boyfriend that was totally into it.