My boyfriend makes up stories and lies on a daily basis. When I question him about it, he swears it's true, even when others say it is not. Is this a disorder? Is he a pathological liar? Please help. I love him dearly. We have been together for 6 months and it is a good relationship apart from the lying.
There are various problems and diagnoses which include lying. He would have to see a therapist in person and ask about his diagnosis if he wanted to know which diagnosis fits him. But his diagnosis shouldn't really matter to you. What should matter to you is whether he treats you well enough.
Start with the assumption that You Deserve To Be Treated Well and then ask yourself if he does or doesn't treat you well enough, including the lies as part of the overall picture. Some people with problems about lying still treat their partners quite well, actually. These people tend to lie because they have very low self-esteem, and their lies are usually about various "accomplishments" they claim to have done in their life, or about how much other people respect them, etc. If his lies are only this type and he treats you well otherwise, it's sad for him. but it's only confusing for you and not terribly troublesome.
If, on the other hand, he lies about drinking too much or about if he's out with other women or something else that has a direct bearing on the relationship, then the lies are only a small part of the problem. The big problem here would be the Truth - that he is indeed mistreating himself and you!
I know it's frequently said, but it's true that honesty is the basis of any relationship. So I think you need to be very clear that if he lies about you and about his relationship with you he is not a good candidate for a long term relationship. (He might often be a lot of fun, kind of as a good friend - but you simply won't be able to count on him.)
I hope this helps. Thanks for writing!