I came here for a different reason to talk about my own problems in a different thread, but let me just say this. I'm 100% sure you're not a pedophile. You know why? Because you're actively worrying and in fear of being one, not to mention you're kaleidoscopic slide down the path of different OCD worries. Just like people with OCD of horrific thoughts of murder or whatever else aren't really murderers or want to put someone into the ground.
If you were a pedophile, pedophiles don't worry about being pedophiles, they just are. It's what's natural to them. You? You're not content with it, it scares you to death and you're going crazy with anxiety just thinking about it.
And then? You overthink about it. You worry so much about it that anyone that fits the description of who you're worried you may be attractive to gets you're blood pumping and you focus in on if you're getting "turned on" by it. And shocker there, a classic self fulfilling prophecy that you think so much about something that it happens Especially something as physically based as anxiety, blooding racing, and getting an erection. Oh, and plus being a teenager. Wow, when I was that young, any girl with a pulse got me going LOL. Baywatch was like a drug to me.

Pedophiles don't worry about being pedophiles. Maybe they worry about getting caught or maybe they worry about trying to curtail their urges so as not to hurt someone else, but they don't worry about the urges THEMSELVES because it's natural to them.
I can't imagine what hell you're going through, but some people here aren't helping with some of their responses. I'm not a professional or anything, but in dealing with my own problems I've had to read a few books on Cognitive Behavioral Therapy and you seem like the exact type of case I always run across with horrible sexual imagery and worrying section.
I highly suggest you go get help, but with as young as you are, I understand it causes just as much anxiety coming forward with this than anything else. Trust me though, medication CAN help, and if you can find a doctor to put you on high doses of sertraline (Zoloft) by just telling you have plain horrible anxiety that would help a lot. It seems like you are already on medication but it's obviously not working, so I would ask to change to an SSRI based medication like Zoloft. Also, go to Amazon.com or eBay and start searching for Obsessive Compulsive Disorder books. I have a couple of old ones right here:
Freedom From Obsessive Compulsive Disorder by Jonathan Grayson and
Getting Control by Lee Baer, if you need suggestions. A top seller list to do with OCD on Amazon should have plenty of suggestions though.
What you'll find is that you can get help and get better, and the key to all OCD isn't suppressing the thoughts but letting them exist and adapting your anxiety response to accept them, and then they go away because they're not causing you problems. The subject matter DOESN'T MATTER. Everyone with OCD thinks they have the uncrackable lock that only they can feel and is so horrific that they could never explain and are doomed, but it's not the case. Good luck, I hope I helped a little.