Went for my yearly it was neg then became pregnant a few months later my test was positive for chlamydia can it become dorment for a long time?

Chlamydia: Chlamydia can persist for several months and sometimes up to a year in the female genital tract. Maybe once in a while longer than that, but it's most likely you became infected between the two test results. But of course you're in a better position than I am to judge if your partner might have had sex with others. No matter what, he should be tested and you both should be treated.