I need to know how to how stop sexual thoughts. It feels impossible to stop; it seems automatic. I also have a strong desire to have sex with a couple of girls in my class and to look at pornography. I am in that part of puberty where my hormones are raging, but I need to stop because I know how bad it is to look at a girl with lust, look at pornography, and have sexual thoughts about girls. I want to live a good Christian life and be faithful to the Lord. So I need your advice.
"No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it" (I Corinthians 10:13).
While it would be nice to be able to just turn off our sexual desire until our minds decide it is the appropriate time, it just doesn't work that way. You can't turn off your hunger until you sit down at the dinner table. You can't turn off your thirst until you are by a water fountain. It doesn't work that way because the desires remind you to take care of necessities when otherwise you might not think of it. And at the same time it is your mind that keeps your desires restrained.
It will be because of your sexual desires that you'll be driven to meet girls and eventually find one to marry. And it is with your mind that you have to keep those desires contained. Just because your body desires something, it doesn't mean you have to follow through on it.
Therefore, you are correct that sexual desire is instinctive and automatic. Looking at pornography is wrong because it is about having sex without being married. It encourages a guy to think only about himself and to see girls as merely sexual objects and not real people. I suspect that the idea of having sex with some girls in your class were planted there by pornography. If you think in terms of do you want to become a father right now with a girl who is not married to you, you would rightfully reject the idea. Yet, children are the natural result of sex and by saying you want to have sex, you are implying you want to be come a father. But few guys think of it that way, they are more interested in getting sexual pleasure for themselves and relief from the urge to ejaculate.
Like Job, you have to control where you look. "I have made a covenant with my eyes; why then should I look upon a young woman?" (Job 31:1). You are going to see things that you rather not see. Such things happen, but you don't have to seek it out or dwell on it. You can look the other way and force yourself to think about more appropriate things. It takes effort, it isn't often easy, but in the long run you know it is for the best.
Temptation is going to be there because Satan is in the world. Fleeting thoughts of doing what is wrong is always going to be present because if Satan can't get you to think about doing wrong, you won't be tempted. However, you don't have to accept those thoughts. It is when a guy dwells on an idea he knows is wrong and mentally accepts it as something that he wants to do, it is then that he moves beyond temptation and into lust. And it is there you have to do battle.