My implant tooth doesn't move or feel loose but it seems to have shifted over the years. Any suggestions?

If the implant is not moving, Chances are the tooth / teeth next to the implant tooth shifted.  Specially if you have pain/ discoloration in the adjacent tooth....you should see a dentist for examination and xray to diagnose the problem and rule out infection on implant /adjacent tooth.good luck 

It is strongly suggested that you seek a competent implant trained dentist, (since your former one retired).  After examination and appropriate xrays a determination of movement or any associated problems can be made...and hopefully if none is found, it will set your mind at ease.

Dental implants cannot move, actually they are anchored in the bone. They cannot have any rotation or protrusion ,no matter how much force you apply. What can be happening, is that the continuous tooth,due to the ligament it has and the masticatory forces. It can be presenting some slight movement ,this will make this tooth, to get proximity to the implants tooth, and also the gum line changes. So an X-ray,and a clinical evaluation would be important. I hope this helps.