Hi! it started after oral sex, 15 minutes after each urination, my urethra starts to burn. all std tests are negative. what? antibiotics only worsen symptoms.

Not an STD: No STD does this. How soon after the oral sex did first symptoms start? No infection (STD or other) can cause symptoms sooner than 1-2 days. Urethral STDs cause pain during urination, not 15 minutes later, and usually cause discharge. Absence of improvement after antibiotics also confirms no infection. This symptom may be psychological or emotional, i.e .anxiety over a sexual decision you regret.