No matter what protection you use (apart from a hysterectomy and abstinence) there is no full proof way of preventing pregnancy. And honestly, there are so many other ways to have sex nowadays that abstinence isn't all that hard. No 'traditional' sex for a year - which for many isn't even a problem - or a child for the rest of your life (barring abortion or other disasters).
But to the original point, there is nothing wrong about being 18 and a virgin. It just means you haven't met the right person yet. Nothing else.