You can't. But by the way you're posing the question you're probably already covering for his lies by adding you own, so if you stop that you're in a way stopping his.
Get a new boyfriend... aim for one that doesn't lie.
If you're truly hurt about lying. then I suggest you get a new boyfriend. A boyfriend is really someone who is willing to listen without further interuption. (I sound like such a retard > . >)
Well, you can start by telling him how it is impossible for you to be able to trust him if he does not stop, but honestly..most people who lie will not stop..they have such poor opinions of themselves that they truly don't believe that you will accept them for themselves. My advice is to accept that he will continue to lie or move on. By the way, the lies aren't because of any of your behavior. Do not accept that from him. He chooses to lie and it is fault and his responsibility. NOT YOURS. Do not accept blame for his lying. Good luck.
Cut his tongue out, or kill him.
If you know that he lies to you regularly...he will continue to lie. Why? Because he is a liar. It has nothing to do with you. He is so unimpressed with himself that he feels the need to lie to make his life more exciting. Either decide you can put up with a liar or move on. He will not ever change.