When we're feeling good and okay about intercourse, when we're aroused, our vaginal openings and canals loosen and lubricate, making intercourse (if we want that) pleasant, rather than painful.
If your partner is over the age of consent, or worse still a legal adult, he could be looking at some very serious criminal charges. However you may feel about these laws, they exist, and it's generally very unwise not to abide by them, especially given the cultural climate when it comes to teens and sex. If you're writing in from the states, there is no state in which you're at the age of consent. First things first: there are all of two or three countries in the world where it's even lawful for you to have intercourse at your age, and in most places, many other kinds of sex.