If you think this is at least slightly serious, I'd talk to a doctor about it. You could also google for the symptom, and see if any REPUTABLE sites list it as a warning sign for something. As always take this with a grain of salt, but it's always good to have information, even if you still have to visit a doctor.
__________________
"Erections lasting more than 4 hours, though rare, require immediate medical attention."
|