PTH stands for parathyroid hormone. Your body needs to keep your calcium level (what would show up in a blood test) tightly controlled because calcium affects the function of your heart. So, if your body is low in calcium, it "steals" it from your bones. Your lab test for calcium would look fine but your bones would suffer. The body does this steal with PTH, so if your PTH level is high, that's bad. If your PTH isn't being tested, there is no way to know whether or not you are stealing calcium from your bones to keep your blood level normal.
So, you need a better level of D (you are barely scraping into the normal range), and you need to know your PTH level. Taking more D is easy,
southernlady has already given you the names of the "dry" products available. Many of us take what would be huge amounts of dry D for a "normal" person but it's what we need. I take 50,000 units twice a day. My may also need to take more calcium, and
DianaCox once provided an excellent explanation of why this isn't what causes kidney stones, which hopefully is somewhere on this website, and her biochem background is better than mine so I won't try to repeat it here.
So first step, get your PTH checked, up your dry D, and go from there.