In consistent Chlamydia results - thoughts? (30M, 30F relationship)

Hi Reddit. I have no one to talk to about this so I’m opening here. I’ve been seeing this guy for 6 months now. 6 months ago we had gotten tested for STDs because a partner he’s had prior to us had tested positive for Ureaplasma. They met up a week before he and I had gotten together. The timeline suggests about 8/9 days. It took 16/17 days for her to reach out and for the both of us to get tested. Now during this testing, Chlamydia was negative on both of our tests. Fast forward 6 months later, he’s tested positive for Chlamydia. He nor I haven’t had any symptoms. He swears that he hasn’t slept with anyone else in these 6 months. I want to believe him as we spend a considerable amount of time together on a weekly basis since we’ve started dating. He claims that his doctors are stating that it could’ve been dormant the whole time and just recently manifested. How is this possible..? We texted 16/17 days after initial exposure. Could that have caused a false negative?