Shrinking penis, impotance, feeling anxiety

Had aggresive (aggressive) prostate cancer, robotic removal 12/01/06.  My penis shrunk immediately.  Why?  My doctor had no explanation.  There must be a reason.  Did 40 radiation treatments in Jan. 09.  Now I dribble urine in bed nearly every night.  Why?  Can I control it?  I exercise my sphinter regularly.  I'm ready to cut the useless thing off.  It's driving me crazy.  Why can't I control bed wetting?  I'm totally impotent; tried shots, pills, pumps, watching porn, everything.  If, when sitting on the toilet, if I don't hold my useless penis pointing downward my stream goes between the toilet seat and the edge of the toilet . . . I pee on the floor.  The accumulation of all this "stuff" is driving me nuts.  I'm 67, have a great wife, and what should be a great life and it is except for a poor attitude to what has happened to me.  I'm not a whiner.  What has happened has happened; it's that simple.  I would love to be told why as to why my penis is such a pain in the ***.  I'm feeling pretty useless.