It is totally understandable. There is a big difference between age play between two consenting adults and BDSM stories written with minors as characters. It is fantasy but we all like to be able to submerge ourselves in the characters and become part of the story. I actually find such stories offensive so I do not read them. My instinct to protect is triggered whenever I read of a child being abused fantasy or not. I think your feelings are quite natural so don't be too hard on yourself.

Jade