@Little_Emily I am very sorry for the trauma you went through as a child. My age play origins/"interests" are similar but, I think, definitely not the same.
I experienced trauma as a child too. My father was an alcoholic, and things were quite bad from when I was about 6 all the way until after I turned 13. I believe that my emotional development was stunted or even halted. So that while my friends and peers matured (emotionally), I saw myself as younger and younger, relative to them. Partially in terms of interests, but more so in terms of seeking security and supervision, rather than freedom and independence. My self concept, has always been that of a pre-pubescent boy. Which fits, even at 13, since I was a very "late bloomer". So, to me the difference between 11 and 13 is mere degrees, not a distinct difference between periods of my life.
I also relate to @drooaygah in that I was fantasizing from an early age as well and, generally speaking, the way I saw/see myself in my fantasies has never changed. Even as I grew older. So, for me, age play isn't something I *do*, it is something that I live. Even when I am "playing" with someone where there is no overt role play, in my mind I am still going to that image of myself as a pre-teen/tween boy, and experiencing the activity through that lens. In fact, that is very true of most things in my life. With friends, with work, with leisure time, I am experiencing them all through the filter of seeing myself as a boy to this day.