Vitamin D3 is a Vitamin that can be synthesised in the body itself.
The skin when exposed to sunlight is capable of synthesising it's own vitamin D3.
Also many cooking oils today are fortified with VIT D3.
You can take twice a week, but I would suggest you have a habit of sitting in the sun for 20 with atleast 20 percent of your body exposed so that body can synthesise the VIT D3 by itself.
Additionally, your pain may not be related to vitamin deficiency, so I would suggest you take a orthopedician's opinion on this once.
Hope you get well soon.