Lack of vit d & bone pain. Can improve.

Hi doctor, My wife has low vit d,latest report it was 16. She has extreme pain bone and muscles in both hands-below elbow with tender sides of palm, and in leg below knee,more severe in ankle and feet. Most of times she is not even able to put her feet on floor without getting severe pain felt which continues for few hours atleast and it's more after waking. She is on d rise 60k for 8 weeks,already 5 weeks dose done and tomorrow is 6th dose. Also having pain killer prescribed which does suppress pain for 4-6 hours but it comes back and remains there until painkiller is taken again. Our worry is even after 5 week of vit d dose,we don't see pain getting improved much. Atleast her severe pain getting into feet on standing is just same. We met Rheumatologist and got RA factor and Anti CCP done both negative. So not sure why her weak muscle and bone/joins are not improving,atleast why pain is always there with simple activities and how she can improve. Thanks a lot in advance.