I don't think it is necessarily an indicator of anything, and rather suspect that since you feel guilt, you're not predisposed to becoming a pedophile. You're exploring what makes you tick, and that's pretty normal for an adolescent. If you don't like it, discard it from your fantasy repertoire, and ... move on ;)
In the event that you have experienced any form of sexual molestation having been perpetrated upon you, my answer is null and void. Although, it still doesn't indicate necessarily that you are a pedophile. But. Seek real help. No matter how hard you think it will be to bring it up, it is nothing compared to how hard it will be when it chooses to bring itself up later on in your life.
I hope Toby and Unknown's answers were helpful to you. Toby's point about you not being attracted to children in your direct presence was a pertinent one, while Uknown's question about whether you yourself have been forced to have sex with an adult as a child would shed some light as to whether or not you had anything to "worry" about. The only thing I would add is you might think about, if you can, neither condoning (labelling as morally good) nor condemning (labelling as morally bad) this sexual attraction to children. Sometimes condemning and repressing (trying to bury) a behavior within ourselves only turns the impulse into a compulsion that hides in the shadows, waiting to overwhelm us later.