it is not uncommon for the urethra to become irritated to the point of causing burning. soaps masturbation/sexual activity lubricants condoms etc. all can cause burning. i am pleased that you were properly tested. a urinary tract infection is uncommon in males but if you are having unprotected sex you are always at risk for an std; chlamydia being the most common.
causes of dysuria other than std or uti. im a 22yo male who went to the urgent care center on 20151010 for dysuria and they did a urine culture and which came back negative for a uti and they sent off a sample to check for std's. im 99. 9% sure that the std panel will come back negative. also about a week ago i had sex and used a different type of lubricant is a week after the "act" to long after to say that my dysuria can be caused by chemical irritation from using that lube? there is not any discharge either.