Is Discharge From Penis Sign Of UTI?

Hi there, I have a discharge from my penis, sometimes it is clear, sometimes it is white, it is not painfull when urinating, it is not everyday either, it seems to come and go at odd times, during the day I feel the sensation that there is a discharge at the tip of the penis. I am sexually active, 99% of the time I use protection, the only time I dont is with my steady partner who has regular check ups and says she is completely clear, should I be worried? Is it just a urinary tract infection that will pass? Thanks for any suggestions.....anything before having to go to the doc's