It is not surprising to have very low vit D at this time of year as you cannot get enough from the sun between october and March, years ago I had a vitamin D test that was on the floor - noone told me this at the doctors only when I asked 6 months later did I find out. They gave me a strong supplement at the time but now I take one from the health shop and try to be religious about it. Vit D is so important so hopefully supplementing will make you feel a lot better, mine was literally zilch but it came up with supplementation and actual sun exposure. I also have a UVB lamp but don't use it that often, at times when I was desperate I would have a sun bed because although they have UVA which isn't great they also have UVB which produces vit D in the skin, try not to worry, low vit D is very common and can make you feel rubbish on it's own without any underlying pathology xx