Its entirely possible to date a pathological liar and never even know. Pathological lying (or Pseudologia Fantastica in psychiatric terms) is a tendency to habitually lie for no apparent reason.

Do pathological liars have feelings?

Researchers argue that while pathological lying may, in theory, occur in people with APD, those with this condition often lie for personal gain or pleasure. A person with BPD or NPD may lie to distort reality into something that fits with the emotions that they are feeling, rather than the facts.