For someone as young as you are, be sure to work with the appropriate doctors to make sure that your vit-D def isn't a secondary issue. Many times with young people, this is the case, and focusing on getting their vit-D levels normalized doesn't have the impact that they'd hoped for.
It's important to maintain healthy levels of all our vitamins for sure. But sometimes we'll miss the primary diagnosis in our hopes that this one fix is our magic cure all. I find myself thinking along these lines sometimes, especially when we get the feeling that our doctors are moving a bit too slow.
i take about 6000iu of vitamin d daily, and 500mg of magnesium. Symptoms sound just like mine were. I'm going on 6 months of treatment now and the first few months are tough, but it will get better if you keep taking supplements. If you live somewhere sunny... Get at least 30 minutes of sun a day! It's the quickest way for your body to absorb vitamin D. also make sure you take magnesium with it... It's necessary for proper absorbtion. it takes 6-12 months to get back to normal. I'm sorry your going through this at such a young age! hope you feel better soon!