I had a very similar problem. However this occurred almost 10 years after my RP/RT. During a routine visit to my Urologist in December I mentioned the flow problem, I wish that I'd kept my mouth shut. He tried to insert a catherter, which he couldn't do so and it hurt like hell. He said that I have a restriction most likely caused by scar tissue. So he said that he'd give me an internal operation, I believe this is called a stricture. I had this op in January this year.
For about 4 weeks the flow was pretty good, then for some unknown reason I became incontinent. And I still am today, going through boxes of pads. This really peed me off as I had never suffered from any incontinent troubles during the whole 10 years, dry right from day one of my RP.
My Urologist believes that he can improve things through another op. However before proceeding further I'm waiting the results of a CAT and bone scan, as my PSA has risen rapidly.
I personally believe that the surgeon has dislodged a clip that was inserted in my bladder valve during my RP, I have a stabbing pain in my groin when sitting. This is a different surgeon who performed my RP. The strange thing is in the past 8 years I have had 2 operations on my bladder to remove stones. No sign of any trouble after both these ops.
So be very careful how you proceed.
You certainly have no PSA issues with a constant 0.03.