Sir few months ago during masturbation I had pain in my penis... After few days later then i again masturbate I had no pain.. but little brownish sperm discharge..Then I stop masturbating for more than 1 month.  After that when I again masturbate I noticed the same problem... then I went to urologist.. he advised me f4 semen analysis,semen culture and ultrasound..Then I done the test... my semen culture, semen analysis reports are normal... nil rbc found... But in ultrasound... small stone in left kidney is found...Dr prescribed be leon 500 mg medicine f4 5 days... now the colour of semen is yellowish with little brown mix... why this happens... can stone cause the change of semen colour...I m not sexually​ active...I masturbate 2 twice in a week..Plz suggest me