tested positive

i was recently teseted positive for clamydia (chlamydia) , i have been with the same partner for nearly 2 yrs havent been with anyone else but he tested negative , why and how is this possible ???

[JessyJames2010]

Both of you need to re-test because of inconsistency of tests amongst partners; test before taking any antibiotics for acurate results.

If we ASSUME you have been faithful then there are 3 possibilities I can think of.
1) you got a false positive (false positives more common that false negatives)
2) he got a false negative
3) he had sex with someone who was infected, and was infected then infected you before being treated and is now true negative.