Thanks for your question and your concern is quite valid. The answer is YES this condition can go undetected for year and even more. As you have not mentioned your sex, I will explain the situation for both. The symptoms seen in men can be subtle mostly or he may experience burning sensation at the time of urination or a discharge that is near to mucous. Some men who are more attentive and ignored the situation have seen to end up in testing positive. In women this condition may lead to serious pelvic infection if left undiagnosed the Pelvic Inflammatory disease. Chlamydia infection can even scar the fallopian tubes and predispose the victim for a tubal pregnancy. In case of women this illness can turn to be more serious if left unidentified and treated in right time. By practising safe practises during sex many of the STDs including Chlamydia would become rare.