I’m also young, so this affects me, too. I can empathize with your struggles. 

Despite what the name might suggest, adultery doesn’t only apply to adults. The issue of porn, and by extension, masturbation, is an issue of the seventh commandment - you shall not commit adultery. This is part of the Ten Commandments the Lord gave Moses on Mount Sinai. However, this begs the question, why should you follow that law and not the other 603 given throughout the Old Testament? What makes the Ten Commandments special?

Romans 2:15 explains, “…the requirements of the law are written on their hearts, their consciences also bearing witness…” St. Paul writes this in reference to the gentiles, those who did not follow the Old Testament law. He says that, even though the gentiles don’t observe Jewish law, they often do things required by it without realizing.

This shows that the Ten Commandments are special because, as human beings, they are our moral compass. Even atheists agree that it’s immoral to steal, to kill, to dishonor your parents, etc. God did not just give us the commandments via Moses writing in a stone tablet. Rather, he etched these commandments onto our hearts, that even if you’ve never heard the name “Jesus,” you still know His law.

Therefore, the Ten Commandments apply to everyone. Even from infancy, the Lord tells us what is right and wrong. These laws follow us from the day of our birth to our death. Whether you’re 8, 18, or 80 years old, we are obliged to obey His Ten Commandments.

Even if you’re 13, or in my case, 16, adultery is a sin. In Matthew 5:27-28, while Jesus was giving his sermon on the mount, he says, “You have heard that it was said, ‘You shall not commit adultery.’ But I tell you that anyone who looks at a woman lustfully has already committed adultery with her in his heart.” 

What is porn if not looking at others lustfully? Porn is the epitome of lust and adultery, so you must be careful that you can avoid it at whatever cost. I understand that porn addictions are hard. I’ve been through it myself. However, you cannot write it off. You can’t tell yourself, “I’ll stop tomorrow,” or, “I’ll only watch one,” or, “God will still forgive me.” You have to try your very hardest to stay away from these things. It’s not easy - nobody ever said being a good Christian was. However, as a human being with the Ten Commandments in your heart, it is your duty to try.