Depends on just where you found these spots.
Do they aslign with your anus? With your penis? With your groin?
Do you have any pimples or moles?
When you work out vigorously, are you chaffing in your shorts?
Are you experiencing a runner's high and not sensing where you have cut yourself?
More info is needed.
Also, is it bright red, still moist, or black and tarry? All these could be from difference areas of the body.
More info needed to help you.
The spots align with the tip of my penis and apparently occur during the night.
I do not have pimples or moles.
No, I do not chaff in my shorts when exercising.
I do not think I experience a runner's high and haven't cut myself.
The blood is dried, a scarlet color.
I'm as puzzled as you, Les.
It certainly would appear to be from your urethra, and occuring over night, possible has to do with noctural erections or early morning wood.
If you have no nicks, tears or obvious wounds on the head, that would seem to narrow it down.
I have no concrete ideas, so I guess I'd ask others here for some input (Medic-Dan, are you listening?).
My instinct is to suggest you see a urologist as this could be a symptom of something serious. I don't know.
You say this happened a couple of years ago too. What did that turn out to be? Has anything changed between then and now? Marital status, new sex partner, technique, health issues? I'm really floundering around here, not sure what might cause this. Anything ring a bell?
(Lastly, are you being especially rough on yourself during masturbation? Or is there any chance that you might be, during your sleep or with a partner? I would think you'd know, or wake up.)