False Negative

I recently had a relationship with this guy and we had unprotected sex countless times for the year we were together. I also found out that he cheated on me several times. We broke up and a few weeks later he was arrested. when he went to jail he tested positive for gonorrhea and chlamydia. We slept together the day before he was arrested. That was 5 months ago and he just told me about him having those STDs. I talked to on of the women he cheated on me with and she confirmed that she caught both STDs from him. I went to my Dr. and they did a urine test for both even though I have never had any symptoms. To my suprise-the tests came back negative! How is this possible since we had sex so many times when I KNOW he had it at the time…..is it possible that I just got lucky? Could the test be falsely negative???