How should I deal with someone who lies and tries to make themselves better than me?

I've known this guy for 6 years and worked with him organizing activities in our church, but I've trusted few people less in my life. It's a very rare thing in our church to not trust people, and because I made myself friends with him I have lost many friends in school, and friends in church. I have gotten angry at him and he has always seemed intimidated by me. He is somewhat of a slacker when it comes to school, but shows an easy ability for memorizing and sciences, but I am more intelligent than him (at least in practice); he seems to have a higher moral code, and when he talks with most people, he jokes around with them a bit pathetically, but when he talks to me, he often is on the defensive, for what reason I do not know, and when I ask him questions, if he feels he can lie about something to make him look better he does (girls usually, says he talks to girls all the time I know he's rarely had the courage to say hello to), and if he has done something wrong (I also work with him and he makes mistakes) he explains how what he did was actually more intelligent when I know it isn't. I have a feeling that I should figure out some way to talk to him and say, "I don't like it when you screw up, but I hate it so much more when you lie about it," or if anyone on here has a better idea. At times he is incredibly awkward and at times he acts as if he is "smooth" then is very embarred, but tries to hide it. I'm not sure if this is from a hypocrisy he hides (our church has high standards of behavior and people can lie about them to church leaders in order to avoid public judgment) or if he's just an idiot. His older brother has similar problems but is more argumentative about it. I care about this guy, enough that I've obsessed over it, but I've got my own problems too, what do you think I should do? Would it make the problem worse for me to tell him what problems I have with him?