how would you tell your parents your pregnant if you were 15 and obviously not married.? but im not saying I am.
well...don't wait until its too late. tell your parents right away and then go see a docter to make sure everything is okay with the baby. sometimes when you're that young your body can't handle the stress of carrying a baby.
You'd figure out what you are doing with the baby and sit down with your parents and say "I'm pregnant". Never wait though because the longer you wait the more mad they're going to be.
Tell them the truth, straight out. Theres nothing you can do now, they may get mad, but sooner or later they'll have to face it.