What is going on here? (General bodily question inside)

Not having any medical background, I might propose a guess that you've developed a significant sensitivity in your prostate, and perhaps the act of contracting the muscles the urinate are somehow also pressing your bladder against your prostate, and by chance forcing it into a "milking action" thereby resulting in the emission of prostatic fluid, perhaps during and of course after you've finished relieving your bladder. Just a guess.

Us older guys get them all the time, mostly when we haven't had sex in a while; it's the built-up old semen being expelled from the body. It started with me in the late 30's, but I haven't had one in at least 3 years or so. There's nothing to worry about, it's just the body telling you that you've held that semen in long enough. Come to think of it, I don't think I've had one since getting a vas.

Wow, and the first time I remember experiencing this was when I was 19. Heh!

I get these all the time. Can't remember when it started for me, maybe in my thirties. Just like you described it, at the end of urinating when it's been a while since I've had sex I'll get this little feeling like more needs to come then I drain out what would appear to be semen, but there's no orgasmic like feeling associated with it. This really occurs if I've taken Sudafed like for a cold or allergies. It's got to be more than just pure prostatic fluid like the urologist massages your gland and makes you produce which is thin and milky, and it's not the clear pre-cum we're all familiar with. I take it to be a mixture of prostatic and seminal vesicle fluids much like what makes up ejaculate.

In the absence of any urogenital infection, I find anything coming out of my penis is pleasurable at least in a measure. Every guy experiences a little residual goo in his urethra (the tube that carries urine and/or cum along the underside of your penis) after sex or even foreplay (at least I do, and others I've talked with). After cumming I always have to watch where I piss, as it may come out of the meatus (the slit in your dickhead) in a split stream, or spray left of right for a second or two until the urine clears out the residual.

After massaging your internal genitals, and often after just being aroused for a while, there's some male fluid of some sort in there. However, the discomfort, if any, should just be transient and not persistent unless it's been a marathon session. Anything present in the urethra causes an urge to void (pee).