Sometimes overactive and "nervous" bladder are synonymous. Associations with outside circumstances, people, places, things and an association with anxiety, excitement or past trauma can set off the urge. We're creatures of habit.
Having to make a phone call can trigger it. Being just fine with your continence during a ride home, car, bus, walking and then as soon as you reach your front door and fumble for the keys BAM! time to GO, sometimes pain, spasms as you fight the urgency because you know subconsciously that home is where the safety and a toilet is. This last example has always been a trigger for me. I've asked around and it seems I'm not the only one. It's an "anticipatory" thing about the urge and the external associations. So it seems.
One good indication is "bladder shyness." When in a public restroom, does your urge to go diminish when someone else walks up to the urinal? Did this happen before you were diagnosed and needed a Foley? Nervous or over-active can go both ways because of the muscles and bladder sphincter. When someone enters the restroom, the "clench" happens, muscles tighten and you retain pee. When you arrive at your front door, muscles relax because you know there's a safe quiet place to pee at home.
Urological medical trauma and surgical trauma associations with procedures can also contribute to how the bladder functions. Then again, it could be lengthy use of the catheter. You might try Kegel exercises as often as you can, clenching and releasing 30 reps with a ten second hold. At least five times per day. You can do while sitting, lying down or standing (the best).
I've read up on the meds mentioned, the side effects didn't seem appealing. I don't know if I'll need them- I hope not. We've been wearing a Foley for about the same time. I'm still using one. I'm doing Kegels now, before surgery.