Is this possible

My boyfriend got tested and everything came back negative. I was told I have tested positive for chlamydia. We're both confused how one has it and the other one doesn't. My gyno told me I've probably had it for a while and didn't know it. But when I asked why I'm positive and he's negative she wouldn't give me an answer, didn't answer my question. We're both going to take the pill but how is this possible? We both know cheating is possible but we talked about it we are not. We've only been together for about half a year.