So this is what I have to look forward to when my son is that age... elliotps932, I know this feels like the end of the world, your stomach is probably in knots, cold sweats, feel like you're going to puke, right? A lot of things depend on your parents. Do you have a good relationship with them? Maybe one over the other? Your dad is going to be your best ally, because your mom simply will not understand. If I were in your shoes, once I got everything taken care of, I would sit down and talk to my dad about it. Just explain to him that you were curious, looked at what was supposed to be "free" porn, thought that the CC was for age verification, but when it billed, you handled it like an adult. This will show him that you are not trying to hide what you did, but you wanted to try to handle it yourself. This will probably work out to the good for you, since your parents will see that you are ready to handle adult decisions and problems. Also, like some of the other posters have commented, he will probably give you a very discreet list of truly free websites that you can visit.
This is not the end of the world, just a chance for you to step up and handle things like an adult. Trust me, this is how I would want my son to handle it, and I would respect him more for coming clean, not getting caught.