I have heard of chlamydia causing infertility. However, the only way for you know if this is the case in your situation, would be to speak with your ob/gyn regarding this matter. There could be a number of reasons why you're having a hard time conceiving...only your doctor can tell you why.
Chlamydia can lead to Pelvic Inflammotory Disease which can cause infertility. It is possible to be asymptomatic. However, usually chlamydia will clear up on its own after a year. (Maybe longer.) It's possible that you just recently became infected w/it (again) because you have been tested in between the birth of your baby and now. If you have not tested positive for chlamydia between your last screening and the screening that showed positive, then it is a newly acquired infection.
The only way to be able to know if you are infertile is to see the doctor. Good luck!