Bone scan tomorrow

This is my first post. I am worried sick. I have a bone scan schedule for tomorrow morning. I've been having an awful pain on the right side of my lower back. It started as a nagging little twinge, then on March 25 I stood up after sitting for about 5 minutes and literally couldn't walk. After a few minutes it got better. But it has been more intense and more often over the last few weeks. It feels like a sharp pain, like the second you pull a muscle or like I'm getting stabbed when it hits me. I imagine it is how a pinched nerve would feel. Twice I would've fallen when it hit me, but I was able to hold on to something and caught myself as I was falling. It comes out of the blue. If I do a lot of moving, it's worse for the next day or so. I am terrified that this could be mets. Has anyone else had anything similar? My radiation onc said he is concerned but its not an emergency. If I injured it, I have no idea when it was. That's the scary part. I would appreciate anyone's thoughts.