Hi, chlamydia can be found inside the vaginal area and also inside the urethra. A swap of the vaginal area could pick up chlamydia and a swab or urine test would pick it up inside the uretha. If you tested negative that should be reliable. Burning inside your uretha when peeing could be a sign of infection but there should be some white puss discharge coming from your urethra as well. With out the discharge i doubt its chlamydia but maybe talk to your doctor about this.