I assume that you have been telling tales since you were a child. Children aren't born liars. They learn to lie because they are too afraid to tell the truth to their parents. It is my observation that abused children learn to lie to protect themselves from further abuse.
Here is how it goes. When a child is punished, beaten, yelled at or treated harshly, he soon becomes terrified to be caught doing anything wrong (for fear of receiving more abuse). When questioned by the parent regarding his/her actions, the child simply lies in order to avoid getting into more trouble. What started out as a self-preservation mechanism soon becomes a problem in its own right.
As you can see, even though you no longer need to lie, the habit is so ingrained that you can't stop yourself. What you need to do is to become aware of the urge to lie, before you actually lie. Get in touch with what you are afraid would happen if you were to tell the truth in that instance. Then, have the courage to voice the fear.
For example, you might say, 'Why do I feel afraid that if I were to tell you the truth about (X, Y or Z) that you wouldn't love me any longer. ' By becoming aware of the urge to lie and then resisting the urge to act on the impulse to lie, you are on the path to healing the pattern.