Ive been diagnosed with chlamydia today. but i got tested in January and it was negative..?

I met my boyfriend back in December, i didnt actually start sleeping with him till mid- January, after i got tested.(results were negative). 2-3 weeks ago i started experiencing odd pains.. i got tested today and turned out i was positive for Chlamydia. The thing is, i never cheated on my BF and i know for sure he didnt sleep with anyone else as i see him all the time. Could it be that when i got tested the Chlamydia was dormant and the test wouldn't detect it? please help i am so confused!