Recently i had anti chlamydia igg positive and igm negative. how is that so as i have never tested for std before and hence never had any treatment?

Unreliable test: Chlamydia blood tests are not very reliable. Your result suggests possible past infection but none at present. Some positive tests are due not to chlamydia, but past infection with chlamydia-like bacteria that cause bronchitis. If you are being evaluated for infertility, your doctor might treat you with an anti-chlamydia antibiotic. Otherwise, probably nothing need be done. Discuss with doctor.