I Was Noticing That I Had Some Yellow Spots On

i was noticing that i had some yellow spots on my underwear ( only after waking up from sleeping ) with a lil bit of soreness in testicles . before two weeks i went to doctor and did urine test , it came out that pus cells and rbc are within the range , doctor said i might not be having gonorrhea but he prescribed antibiotics , can you just tell me what are the causes of the spots in underwear without having gonorrhea and having normal results in tests ? im really concerned about it