What kind of vit D supplement were you taking, and why only weekly? I have struggled for years to keep my vit D levels up and I take 5000IU/day, which keeps it in a happy place (100+/-).
You can also get it from things like salmon and eggs, not just milk. It's fat soluble, so best to take it with a meal with a good amount of fats in it, or take it in a gelcap form - I take this. Make sure you take D3, not D2, as D3 is the form that's naturally occurring in the body.
I certainly wouldn't just give up on it because it's not working, if I were you. Vitamin D deficiency can lead to a whole host of other issues. What were the studies you read that convinced you to stop taking the supplement?