Men with this symptoms usually are just internally massaging the prostate gland and/or seminal vesicles with the straining at stool and/or the pressure of feces against the prostate gland as it is expelled. Normal prostate gland secretions can be cloudy/white, or if the material is from the seminal vesicles, it may be semen. This symptom normally normally isn't a sign of any STD, especially in the absence of spontaneous urethral discharge, urinary discomfort, etc.
This is not my area of expertise, and you might want to see a health care provider for confirmation. Or consider posting the same question on the MedHelp urology forum.
Good luck-- HHH, MD
Since I was a teenager, every once in a while, I would feel intense burning, not during but after urination. It felt as if I had to go, but then only a little would come out, and it burned. Sometimes, I'd pulse and a milky discharge like seminal fluid would come out.
I've been tested for STDs and had none. Currently, I'm not sexyually active, and have not been for over 10 months. Off and on, I'll have the symptons. Sitting here, I felt this pulsing, and some discomfort.
I'm on a somewhat high protien diet. Other than that, there's no other reason. Sometimes, after an orgasm (whether self-induced or otherwise), the symptoms will occur.
Tim