What Causes Muscle Ache In The Legs?

Hello. I have had muscle aches and pains in just my legs for 3-4 years. I have been a regular exerciser for 30 years and a group fitness instructor for 25 of those years. I teach both cardio- and strength-based class formats and, therefore, am familiar with exercise induced muscle soreness. The pain I have been experiencing is unlike normal muscle soreness, is chronic and has become progressively worse over the years. Neither my primary care physician nor my orthopedic specialist, with whom I ve seen for prior acute knee and back concerns, were able to determine the source or cause for my pain so I began to assume the pain was due to years of wear and tear from exercise as well as the aging process. However, I refused to give up. As a result of my 2017 annual check-up and blood work results, my primary physician referred me to a rheumatologist. Nothing out off the ordinary revealed itself. This year, my new primary ran an exhaustive blood work-up which, again, showed abnormal levels and referred me to another rheumatologist. Based on that check-up, I was prescribed a high dose vitamin D regimen. 5,000 mg. per week for four weeks. I am on my second week. I have confidence in my course of action but can t help but wonder if I am missing anything. Thanks.