Dear service user,
Thank you for writing to Healthcaremagic. I can understand your concern.
The symptoms you described are not suggesting any disease.
The fluid which comes out during urination is fluid of sex organs and tiny glands in the way of urine tube which may come while straining during defecation. This is absolutely normal thing. This fluid protects from infection in urine tube.
This fluid is not semen. It smells fishy because of 
prostate fluid. Semen do contains prostate fluid so it smells fishy.
Semen comes out only in three situations hence climax of intercourse, 
masturbation climax, night emission.
Night emission of semen is again, not a disease. It may occur at any age. Nothing to feel strange!
Semen is being produced by genital organs continuously but, it has to be expelled by some means. This situation is just similar to a glass of full milk to which you add more milk, with the logical result that it overflows.
Similar happens to semen in body.  If one neither has sex nor masturbation for long time, semen gets accumulated in its pouch, so it gets expelled in the form of night emissions, which is normal.
Increase frequency of intercourse or masturbation will empty the pouch of semen and night emission will not occur.
Semen is just akin to other body fluids like saliva, tears and blood.
It is produced continuously and gets utilized.
Loss of semen in nightfall, during sex or during masturbation does not have any adverse effects on body. No need to see doctor for this. No medical issue.  No medications needed. No need to worry. Relax and go ahead with happy sex life.
Wish you good health.