Of COURSE you should tell your doctor. Not "mention it". TELL him. Tell him that you are experiencing bladder incontinence, particularly at night (if that is the case), or however often it occurs during the day that you either pee yourself, or have to dash to the bathroom, barely making it. And if you're experiencing bowel incontinence, or having to have bowel movements that you haven't planned for.
He (or she) is a DOCTOR. They've seen/heard/experienced everything in a patient, and you are no different. This kind of information is essential for him to make some sort of diagnosis. It may be that he'll send you to a specialist for a test to see just what specifically is causing your bladder problems, but there are meds you can take for this that will make you MUCH more comfortable, and in control.
Same advice for you, Braygirl. If you're dealing with bladder incontinence there are meds that can help you control it, whether you have numbness "down there" or not.
And...girls and boys...we are ADULTS here, with very real medical problems. We need to learn the proper words to describe our problems, and not use euphemisms like "down there".
...I am not a doctor, nor health professional, and don't pretend to be one, here.....