I recently had a crown put on an upper bicuspid.  It seems to be quite
pressure sensitive now.
 I'd expressed concern that there wasn't very much exposed tooth left
to put a crown over, but my dentist said it was "very crownable", and I
believe him.  He is a very good man.
 Not long after having it put on, I was unconsciously gnashing my teeth
from side to side and it seemed to "move" slightly; now it doesn't mesh
squarely with the bottom tooth.

 I don't know if it was the whole tooth that moved, or the crown on the
tooth.
It doesn't seem loose, and hasn't moved since!

 It's not sensitive to temperature or anything else--just pressure.

 I don't know if the pressure sensitivity existed before I "moved" it,
since it was within about a day of the intital installation of it, hence
it was still kind of sore anyway.

 I almost feel embarrassed to go to the dentist again, since he's so
busy and I feel like I messed up his handiwork.  Or maybe I'm afraid of
removing and re-setting the crown on a tooth which is so compromised to
begin with.
 Will I probably end up damaging the corresponding (bottom) tooth if I
don't address this?  
 Has anything I've described sound like a cause of this pressure
sensitivity?
 What IS normally the cause of it, when other kinds of sensitivity are
absent, (hot, cold, etc.)?
TIA