Chlamydia

So I got chlamydia from my ex sometime in 2015-2016, we broke up and I started dating my current man November 2016. In September 2017, I went in for a regular check up and found out I had the STD. My man and I had unprotected sex from Nov 2016-Sep 2017 and he came back negative. How is that possible? That's almost a year of unprotected sex and he didn't get it.