Op really isn't doing anything wrong, he was asked to do something and he did it. His biology just kicked a little and he ended up noticing what any MAN with a fucking set of BALLS would. A girl on the way to becoming a woman...and really since we spent CENTURIES banging chicks around that age or close to anyways, it is kinda ingrained in the genetic code.
That being said, OP, guru is right, I've tried to think of something more to say to it, but I can't he's covered all the bases and has the BEST advice I've ever seen really on the subject
