The size, length, colour, shape of every woman's labia differs. And chances are there is nothing wrong with your labia. You are just shaped differently.
Just like how we cannot all have the same kind of nose, face shape and eyes, we cannot all have labias that look the same.
For more information, check out Pink Parts - Female Sexual Anatomy
Of course if you want to put your mind at rest, you could always mention your situation to your doctor or gynecologist.
Here are a couple more threads on other posters who have asked similar questions to yours.