this site is devoted to parcopresis (shy bowel). anyway, from my own experience of shy bladder, this might help with your condition (which though not shy bladder is related):

you're urinating in small quantities. either this is because of a physiological problem or a psychological one.

best to get yourself checked medically to eliminate the physiological possibilty.

if you're all clear on that front, then try gauging to yourself on a scale of one to ten how full your bladder is (one is no urge, ten is full to bursting). then make sure you don't go until you reach a level seven.