Hi @greff, I also have osteopenia and my doc told me I need to take 1200 mg calcium a day. I tried it for a couple of weeks but it made me so constipated I stopped taking it and really try to eat more foods with calcium and drink more milk which I rarely did before I was diagnosed. Here's a good article on the subject:

Calcium and Bone Health -- https://www.helpguide.org/articles/healthy-eating/calcium-and-bone-health.htm

95% of people have too much calcium in their body (from eating cheese, etc.)and not enough magnesium or.phosphorous. They need to be in a 2:1:1 ratio.
Excessive calcium intake results in it building up in the soft tissues, causing arthrtitis, cateracts, hardening of heart valves, and so on.
Natural Vit D3 is important. Blood levels should be around 40-60, with it mostly coming from daily mid-day sun exposure. Optimal levels of Vit D (and all the benefits that go with it) are just biomarkers of how much sun exposure people get, per a large Norwegian study.
Vit K2, found in fermented foods is what drives the blood calcium into the bones.

Celiac is a usually from antiobiotic resistant Strep in the guts. It LOVES gluten (and often eggs & dairy, too) and causes great inflammation when fed it's favs and multiplying like crazy. Starve it out by going mostly raw vegan for a few weeks. No gluten, no dairy, no pork, no eggs, no refined sugars or refined vegetable oils. All the organic fruits, berries, colorful vegetables and herbs you can eat as soups, smoothies, salads, etc. Any meat protein to be eaten in the afternoon, not morning.
Will need to eat or snack every 1.5 to 2 hours to get the needed 2000+ calories a day to sweep those toxic dead strep bodies out of your guts. Drink only lemon water and herbal teas. Minimize patent Rx & OTC meds since they stress the liver and gut biome. Have steamed sweet potatoes at dinner as much as possible.
You will also lose any excess weight as a side effect.