Thirteen year olds do DUMB STUFF. You're not 13, anymore.
You worry that you're capable of doing sexualising a little girl. Well, yes, you are. So am I. So is anyone. Don't confuse being able to do something, with wanting to do it. I have harm OCD. With intrusive thoughts of, well, killing. Am I able to carry those thoughts out? Easily. Do I want to? Well heck no. So I don't. And I make the deliberate decision to not worry about what I can do- only worry about what I have done. Which in this case, is moot- because I haven't nor am I making any plans, to commit murder. I'm have made the decision to not worry about intrusive harm thoughts; I have made the decision to not worry about something that hasn't happened yet. There's no magic to this- it just requires being obstinate on my part, and making the decision that I will not worry if I get a harm thought, and that I won't perform any compulsions to keep anything bad from happening. Because I've made up my mind, that I'm not a murderer, and I'm going to do no such thing, end of story. And because of that, I won't worry about it until I've done it. Then, I'll worry. Not before.
And it wasn't long, before I started being less distressed by the thoughts- plus they don't come up as often, either. Now, when one does, every time I have a choice- to worry about it, or to deliberately ignore it and decide I don't care about that thought. And I know- that if I worry about it even just a little, then I'm going to be letting it make me anxious again. Whereas if I ignore it... five or ten minutes later, I don't even remember getting the thought. Every time I write about this in forum as an example, I.... get the thought. And I have to do it again- ignore it. Five minutes from now, I won't be thinking of it, at all. It just takes practice, practice, practice.