Another thought is maybe the form of D3 you're taking isn't a good one for you.

You can get D3 from Cod Liver oil, but it's not recommended by D3 researchers because the high amounts of retinol in it can be toxic, cause bone loss, liver damage and also possibly blocks the D3 from getting used properly.

Also you can get D3 liquid capsules, which one doctor recommends.

You can also get D3 from lanolin sources (sheep). That's what I'm currently taking. It's a capsule with dry stuff inside.