I've been having a strange issue for a few years now. Almost immediately after ejaculation, a sense of pressure and even uncomfortable/painful burn/tingling feeling can be felt in the tip of my penis. It can be somewhat lessened if right as ejaculation starts, I stop all stimulation to the penis, thus somewhat lessoning the orgasm itself. If I do this at night, and go lay down in bed, after a short while I will begin to feel a painful tingling in the tip of my penis, which will start to make me feel like I need to pee, and I will sometimes even have to actually go pee.
Note this sensation does not happen any other time.