Kind of a shot in the dark, here, but you don't happen to have any digestive issues, do you?

Undiagnosed or otherwise unmanaged conditions can increasingly compromise the body's ability to absorb nutrients, resulting in malnutrition problems like osteoporosis, weight loss, etc. I know with celiac disease in particular, the ability to digest milk arises early on, to the extent that it people with it can get misdiagnosed as being lactose intolerant, when they're actually experiencing a result of the autoimmune damage to the small intestine.

And, of course, inability to digest dairy products can greatly reduce absorption of calcium and other minerals that make for strong bones....