Could the pressure when standing, painful sex with deep penetration, and trouble urinating be symptoms of a uterine prolapse? other possibilities?

Yes.: Pelvic organ prolapse can be associated with all of these symptoms. This is especially true if you have had previous vaginal deliveries. Other problems such as a mass in the pelvis can cause similar symptoms, but are less common. Be sure to be seen by your gynecologist.

It is possible : But there are several different problems that could cause your symptoms. You should be evaluated by a gyn to find out more.