OHHHHHH YESSSSSSSS. You are describing me me me right down to the tail bone thing.
I've been to the Chiropractor and he says its my siatica nerve in the back, but he thinks the MS is playing havoc with the nerve. Sooooo stretching those butt and leg muscles is so important.
The leg thing I describe as "hitting my funny bone feeling" (only not so intense) Its a sensation that drives me crazy more than anything.
Try taking a magnesium/calcium supplement to see if you get some relief. Otherwise when the feeling gets intense in my ankles and feet, I rub CAPCASIN on and it seems to help. warning (Capcasin cream is potent and you don't want to touch any other part of your body until you wash, wash, wash again your hands)
The back and hips will be greatly helped by some excercises. Look at the link below. I get the most relief from the three exercises under "hamstring" stretches.

http://www.thedietchannel.com/Sciati...p-Sciatica.htm