Suggest Treatment For Penile Itching And Discolored Sperm

about one month ago, I received oral sex from let me say, a questionable woman. About 3 days later I experienced an itching sensation followed by slight discomfort when I gently squeezed my penis in the center. Now I have discolored sperm that appears brownish yellow in color and more watery than thick and white like before. I am afraid I have contracted an std. I have no burning or discharge though. Please help