Chronic pain causes difficulty in urinating?

I am 40 years old, and have lived with moderate chronic pain from a back injury. I began noticing problems urinating about a year or so after I hurt my lower back, and subsequently developed an inguineal hernia, which required surgery to repair.

I have been under the care of a urologist since the hernia repair, and he assures me that I have a normal prostate, but that my urinary hesitantcy has nothing to do with my prostate. He assures me that my bladder neck sphincter is 'very toned', and constant pain will cause me to 'clench' down on it, causing it to remain tightened and constrict the flow of urine. The problem is that I have some pretty bad pain in the area of my genitals, across the perineum, and around my anus. This pain is quite severe sometimes, like I was riding a bike and missed the pedals, comming down hard on the cross bar (men who have done this will know how it feels). It usually comes from sitting on something like a wooden chair, or on the edge of a seat.
My question is this: can I rely on the urologist to be thorough enough in his exam (he examines my prostate every 18 months or so, coinciding with my refill of Flomax and Terazosin Rxs)? I don't want to wait too long to question his treatment, but don't think that things are 'normal' down there.

Does anyone else have this affliction, and if so, how do you get treatment?

Thank you.

Brian