About four months ago i started having the same (or very similar) urinary issues you are having. . .was getting quite annoying. Went to the urologist and she did some tests and says I have spastic bladder - essentially, the signals of when it is full get confused. . .so, when there is very little in there it thinks it is full and/or when full it doesn't always send the right signal.

She prescribed Sanctura RX and it has worked great. Most of the time my bladder functions like it used and when it doesn't it is much more milder than before.