ce28 – Welcome to the ThisIs MS community.
To answer your question, "could this be an early sign of multiple sclerosis?", Yes, it could be. But there are MANY other conditions with similar symptoms.
You and your doctor have begun to examine and eliminate these other possibilities. The test of your vitamin D level is a good beginning. Continue to work with him, testing for cortisol level, glucose and insulin levels, the thyroid hormone levels (TSH, Free T4, Free T3, Reverse T3, and antithyroid antibodies). Ask for your own copy of the test results and keep your own file at home.
All the best to you.
My hypothesis: excess insulin (hyperinsulinemia) plays a major role in MS, as developed in my initial post: http://www.thisisms.com/forum/general-discussion-f1/topic1878.html "Insulin – Could This Be the Key?"