I had a chlamydia test done a year ago via swab, this was a month after alleged encounter. tested neg. how sure can i be it wasn't a false neg?

Here are some...: If both partners are tested, treated, and followed without recurring symptoms & further encounter out of one-to-one relationship, it is reasonable to clinically declare your are okay. This is life reality although many STD-affected with chlamydia & gonorrhea are free of symptoms. However, it is also reasonable to be retested annually if you are in high-risk category like one with multiple partners