Your D3 is severely deficient. I was at 19ng/mL in September and will retest my blood in a few weeks.
You may be taking D2. That is bad. You need D3 and taken daily, not weekly or monthly.
US lab range is 30-100ng/mL. You need to be above 50ng/mL. Anything below should be considered deficient.
UK range should be 150-250nmoL
D and magnesium deficiency can cause depression, fatigue, anxiety, pain, brain fog, headache, eye sensitivity, etc.
You need Vitamin D3 supplements, magnesium and Vitamin K2 (as long as you aren't taking medications that would conflict with K2).
You could start at 5,000iu D3 daily for a few days to see how you feel, then work your way up to 10,000iu daily. Even when you get to corrected levels, you need to supplement daily. D3 does not stay in your body.
5,000iu is more like anaintenence dose. You must retest your blood after 3 months to see where your levels are at.
The only blood test that can diagnose vitamin D deficiency is a 25-hydroxy-vitamin D (25 OH vitamin D). Unfortunately, some doctors are still ordering the wrong test, 1,25-dihydroxy-vitamin D.
Magnesium is essential, you need to take it with your D3. Take D3 with some sort of fat (like coconut oil, avocado, peanut butter, etc. it helps D3 & K2 absorb). Take D3 in morning or afternoon. Not at night. It may keep you up.
I had what was considered low in the UK at 30! At 25 you are in danger of getting rickets.
My doctor put me on high dose Vit D for 8 weeks, retested at 111. The 'normal range' is 50-200 in the UK. As we don't get much sunshine the ability to get enough to make your own is limited.
Everywhere in the world people are scared of skin cancer so plaster sun cream on - we do need some unprotected sun on face/arms it depends how hot the sun is where you are - might only be one minute or twenty minutes depending where you are.
I'd see your doc and perhaps have a look re low Vit D symptoms, it does take a while to get your levels up though.
Hope this helps.
Thirty is the minimal. Many people test at 40. Get those levels up with oral supplements! The "fifth" pill of 1000 mg won't do ungotz. Many physicians start with 50,000 IU.