You are definitely overreacting. I don't know why it is that so many people seem to think that nurses are required to open needles, equipment, etc in front of a patuent. That's not true. If you have OCD type issues, then request that the nurse open everything in front of you. However, with the nature of these kinds of obsessive thoughts, even that is not usually enough to stop the irrational thoughts.
Nurses do NOT reuse needles.