I would also echo getting tested first is vital. Don't assume (or let your doctor assume) that you have low levels of Vitamin D.
With that said, not only do I have low levels, but once I stop supplementing, my levels drop every time. Grrr! But I came across this article that just might explain why it is for me and for many others here:
ihateticks.me/2015/10/27/bone-pain-and-funny-levels-of-vitamin-d-all-about-the-parathyroid-glands/ It's a really good read, and explains that deep bone pain that some of us get.