I had blood test for Chlamydia. Result says IgG Ab >/= 1:16 and IgM Ab < 1:16. Does it mean that I had it in the past but not currently?

Maybe past infection. The chlamydia blood tests are pretty much useless. This only indicates you have had infection sometime in your life with chlamydia, or with related non-STD bacteria. (For example, Chlamydophila pneumoniae causes bronchitis etc, is very common, and also give pos result on the blood test.) It's a useless test to diagnose current infection. If at risk, you need a vaginal swab or urine test.