Well, Witch, a lot of factors come into play here.
First of all, we all get turned on by different things, and sometimes these things change through different stages of your life. For a while, you might find one thing intensely arousing, and then move on to another thing. In this case, has this always been the only thing that turned you on? Is it hurting you or making you want to put yourself in harmful or illegal situations (wanting to have sex with very young girls, or have sex with your father or uncle)? Or is it something that just turns you on in pornography, you masturbate, and get on with your life?
Pornography seems to be an extension of fantasy for many people. And the thing about fantasy is that it's not something you are actively involved in. It's not real. I'm willing to bet that these movies and pictures you're finding online aren't really of very young girls (they're more than likely of legal age) and that the men they're with aren't their fathers or uncles. It's the idea of it all that's exciting to you, right?
I would venture to say that unless this in itself is causing you discomfort or harm, it's okay for you to look at what turns you on. However, if you feel you're becoming obsessed by it, or that it makes you want to put yourself at risk of doing something harmful or illegal, it may be time to talk to someone like a counselor about it.
~lemming, Scarleteen Advocate
this is what you get for liking it.
"The best-looking boys are taken, the best-looking girls are staying inside. So, Judy, where does that leave you, walking the streets from morning till night?" --Belle and Sebastian, "Judy and the Dream of Horses"