I suspect you're being too hard on yourself. I give you loads of credit for recognizing and admitting that your lying is a problem. I don't think the cause is any deeper than what's been posted here...you probably lack self-worth and want people to think you're the person you want to be, the person you believe they'll like.

Maybe it will take a bit of practice to stop lying. With that practice I think you will develop a habit or truth-telling - or of not giving away much personal information at all. My biggest concern is what I mentioned already...that people will avoid you because they can figure out that you have a habit of stretching the truth. But you can break that habit and exchange it for a habit of genuineness, I really believe you can!