Hiyer,if no condom was used and 1 of you had chlamydia the other would catch it whilst having sex.Sometimes there are no symptoms what so ever,there are probably millions of people walking around with it not knowing.Its worse for women as it can cause fertility problems and in worse case may not be able 2 have children.Antibiotics from the doctors cure it,but always use a condom to protect yourself its not worth the risk. Hope that helped youxx