Help please

I am freaking out & just feeling so low. I’ve been having weird symptoms of nausea and things for a while but finally decided to go to the doctor about it and was told I had a UTI. I asked to also have an sti screening and the doctor did so. As she did such she said that everything looked fine and it seems to be just the uti. So a day later I get a call saying I have Chlamydia and I freaked out because I have only been with one person... my bf for over a year. So I called him and he said he hasn’t been with anyone else since January of 2018 but in May of this year that person had her yearly check up and told him she had Chlamydia. He tested negative for it. He also said in the past he had it but it was treated. He swears he has only been sleeping with me but I didn’t have anything before this relationship. I just want to know is it possible for him to have had it for a year without knowing, because I don’t even know when I got it since I’ve only been with him and didn’t have symptoms ? Is it possible for him to test negative and me to have it? Could he have not been fully cured from when he had it and it just came back? I want to believe that if he was cheating he would own up to it at this point.