Vit-D deficiency. Please suggest.

I have joint paints on both the hands for more than one year. I consulted Orthopedist and went through some medication. I also went through some physiotherapy treatment. But none of them helped me, they just gave me some relief but not completely. In last one year did my Vit-D test thrice and it was always below 15ng/ml. Once an orthopedist adviced me to take vitamin D medicine once in a week for one month. After taking this I had some relief for few days and the problem started again. Now I have severe joint pains and dizziness. When I checked my Vit-D last week it was 16ng/ml. I am thinking my problems are due to Vit-D deficiency. Can some one please suggest which specialist should I consult for Vit-D deficiency and will Vit-D deficiency causes this kind of problems. Please suggest. Thanks in advance.