Of course you are worried. I’m sure you are beside yourself about this. No, what he is doing is not “normal” as in “usual.” Yes, you should be concerned. It is normal for kids to be curious about what the other gender looks like and to want to see. What concerns me is that your son seems to know what oral sex and intercourse look like. Who would have shown him that? He says he saw it in a movie but why, oh why, would anyone let a 4-year-old see a movie that includes explicit sex? That doesn’t make any sense to me. I’m deeply concerned that someone has been molesting him and he is showing you what has happened because he is afraid to tell. It’s not uncommon for a child who has been molested to repeat the behavior rather than tell because the abuser is often smart enough to threaten or bribe the child into silence.
I think you should make an effort to talk to your son, calmly and lovingly, about the idea that sometimes kids learn to touch other people’s privates because an older person has shown them how. Explain that you understand that sometimes kids are told they will be punished in some way if they tattle. Let him know that you won’t punish him no matter what he says. Ask him again where he saw the movie and if someone has taught him what to do. Watch his reaction carefully. Stay calm but serious. Let him know you love him. You may need a therapist to help you with this, especially if he comes forward with upsetting information.
I certainly hope I’m wrong. But if he has been molested, it’s important to get professional support right away. He needs to know you’ll keep him safe. He needs to be relieved of the burden of the secret. And he needs age-appropriate sex education. Meanwhile, you are going to need some support.
I wish you well.