Chlamydia twice but no sex?

I had chlamydia from my cheating ex for about a year undetected. Got treated, and got a ton of tests just to be sure that all came back negative. Then I started experiencing pain again. So I went to the doctors, no chlamydia found. Went to the doctors again due to more pain, and they detected chlamydia...! Even though I use protection, AND my partner tested negative (went with him to doctor’s to confirm results). What the heck? Has anyone ever experienced this? Is that even possible? I know y’all aren’t doctors, but maybe someone here knows someone who knows someone who’s experienced this...!