Good evening doctor. My partner of 4 years and I recently went to get tested for stds and he came up positive for chlamydia. I came out negative. He swears it's only been me for 4 years. Is there a possibility that the test could've been a false positive?

False Positive. No test is 100%. There will be false positives and false negatives. You can always get another test. That being said, if you both have been monogamous for the past 4 years why the tests? Just food for thought. Additionally, if you have had antibiotics recently it could gave cured any infection you had. Remember men usually have no symptoms.