It may be that your boyfriend didn’t tell you about his son because he was afraid that the information would make you lose interest in him. That might explain it, but it doesn’t necessarily forgive it. Honesty and trust are the basis for a good relationship. If his withholding and lying about the boy undermines your trust in him, it will be difficult to regain it.
That being said, you mentioned another important issue in your letter. You are also concerned about the difference in your sexual history. You said it is “too much” for you. Trust yourself. If it is important to you that you be someone’s first and only, then you may need to take a big step back from this relationship.
You are young. There is no rush to find true love or to get involved sexually at your age. There are men who, like you, are waiting until they are older (and until they find the right person) before they have sex.
I wish you well.