My doctor told me chlamydia was gone even though it was untreated. how is this possible?

Depends: I'm assuming that you were tested for chlamydia and it came back positive, you were untreated for this chlamydia and then you had another test for chlamydia and it came back negative? This seems very unusual. It's common for women with chlamydia to not know they have it, but i haven't heard of it spontaneously going away. The 2nd test could have been a false negative. Check with your doctor.