Hi Paul, welcome back!  Osteoporosis doesn't usually cause pain in any area unless you have a fracture.  Of course there could be other medical problems going on like arthritis, muscle spasms, from over doing things, so you should ask your Dr. to order an x-ray to see why you have this pain.

When you had your last dxa, did they include a vertebral fracture assesment (VFA)?  Here's an article on screening for fractures with x-rays and VFA's. This is one way to screen for fractures when you have a dxa, and it's something to consider since it will tell you if they are any structural problems with your spine.  Many dxa's include this test now, so it's just a matter of finding out ahead of time if the imaging center you are using includes this test with each dxa scan.

I'm so sorry you are still dealing with the ONJ.  Good luck with this, I hope your Dr is able to help you resolve this soon.