– like on an airplane, when you get a "bubble" in your ear – that doesn't go away for about 5 minutes. Why is this?
My guess is you are doing something with your mouth and tongue that's either forcing a little bit of air into your Eustatian tube (which runs from the throat to the middle ear), or sucking a little bit of air out of the tube. When there's an air-pressure imbalance between the two sides of the eardrum, you get that "bubble" you mentioned. Next time you ejaculate, try holding your mouth wide open with your tongue all the way down (as if you're yawning) and see if it still happens. If you conclude it isn't a matter of air pressure, or if it also happens during other forms of physical excitement (such as during intense athletics), it might be worth mentioning to a doctor.