Sensation of urgency to pee only when I sit down in a chair or in a car. Very bothersome it makes me go to the bathroom What could it be from? Thank you doctors.

Here are some... If urinary urgency is really related with positioning as described, all you can do is make sure of emptying, avoiding consuming bladder irritant-containing foods or beverages, and optional use of anticholinergics before sitting in to drive. Of course, try to void timely-not waiting until last minute. More on men's voiding trouble? To Best..
Constipation. It could be due to constipation, a full large intestine or it could be due to pressure from the prostate. Either way, I would actually get this examined by a doctor in person. A prostate exam would be helpful. It could be because your bladder isn't emptying all the way but in rare circumstances it could be that stool from the intestines or something on the large intestines is creating pressure.