What Causes Urinary Incontinence?

I have trouble with my bladder. I feel I have to go (feel it leaving the bladder) and have to rush to the toilet hoping I make it in time. It is usually a small amount, just like it is only from the urethra. In the past I have taken pills to relax the bladder. I think the name is Detrol. I took it for several years but felt it wasn't doing any good. I've taken others for a short time but never satisfied so I quit. Also I had eye problems and was told I have dry eyes. I assumed the pills were causing this. I also urinate frequently (only a small amount). Other medical history: hydrocephlitis (can't spell it). A shunt was implanted in 2007. Don't know if all that information is necessary.