Why Lie?

I hate when people lie. I mean there is a difference between a white lie and a lie. A white lie is just something little that WON'T hurt someone in the long run but a lie is something that you use to get out of a predicament and hurts you and/or another person in the long run.
I just hate the fact that people lie and get caught up in the lie and then try to deny it. They think their slick though, cause it's a lie, so when you want the truth they had time to think and get an alternative answer to what was really going on. Or even lying to a person about another person. For example my boyfriends ex(still obsessed over him after 6 months) tells me all the time that they seen eachother whether it be at his work or he went to her house or something like that so then it goes to me asking him what the truth is. Don't forget I'm either at school or work when the stuff she talks about had happened. So then he tells me what he tells me and of course I'm going to believe him but that lie is always going to be stuck in my head. I am constantly pondering on what really happened. He's been telling me that I'm going to let her break us up(cause thats what she wants obviously since I have him) cause I believe what she says but I go into I'm not believing it, I'm just thinking about it. So that's why I hate lies cause I never know what to believe.

What do you think? Do you lie to get what you want? Do you ever think about a lie later and wonder if Karma is going to come around? Let me know...