confused1,

It is not unusual for truthful people to fail a polygraph "test." Polygraphy is a scam: it has no scientific basis, and the only ones claiming it's valid are those who are those with vested interests in the perpetuation of this scam.

You'll find the stories of others who have wrongly failed the polygraph here. See in particular the statement (PDF) of Gary Smith, who like you wrongly failed a "fidelity" polygraph.

For more about polygraphy and the simplistic assumptions that underly this pseudoscience, see our e-book, The Lie Behind the Lie Detector (1 mb PDF).